Tag Archives: MEAN

MEAN web development #9: Some last remarks

So by now we’ve seen the full MEAN stack, MongoDB, Express, AngularJS and Node.js. Additionally we’ve seen the templating engine Jade in action as well as used Socket.io for real time web applications. If you combine that with my earlier series on ‘vanilla’ web development you’re already a pretty versatile web developer (well, dependent on how much you practiced)!
In case you missed a MEAN article, here they are:

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

In this post I’m going to discuss one topic we haven’t covered yet, deployment. Next to that I’m going to give you some alternatives for the technologies we’ve covered in this series.

There is no GitHub repository for this article as there won’t be any code samples.

Deploying a Node.js application

So we haven’t talked about deployment yet. Not even in my web development series. To be honest, deploying software is not what I do, I just write them. Besides, deploying to the Windows laptop you’ve used to build your software is a bit difficult and in most¬†cases isn’t even close to actual deployment. Unfortunately I don’t have any spare web servers laying around ūüôā
That isn’t to say I can’t point you in the right direction.

Node.js is a little different from what you’re used to. Consider the PHP application we wrote earlier in¬†Web development #4: PHP in the back. We wrote our page and got it up and running using XAMPP, where we specified the port and other settings. The PHP file¬†didn’t do anything. Likewise, a C# web application doesn’t do anything until you host it using IIS, which can be configured however you like.
That’s different for a Node.js application. After all we specify the server, where it should run and how it should run in our JavaScript file. And then we could run it from the console. On production environments we really don’t want to run a console though. We probably want to host our application on port 80, which is the default HTTP port, which requires an elevated command prompt. So someone with admin rights should log on to the server to (re)start our Node.js app every time something happens (either the app crashes or the machine is restarted). That doesn’t sound very appealing…

So we could simply write some command script using a loop that restarts Node.js whenever it crashes and start that up, with elevated privileges, either using a service or the built-in scheduler. That solution has¬†some serious limitations though. What if your app goes in an unrecoverable state, making it crash in a loop? Or what if, for some reason, it hogs up all of your memory? A command prompt can’t really give you a detailed log of what’s happening with your application.

That sounds really tiresome and messed up. Luckily there is a better alternative. You can use PM2 (Process Manager 2) to run Node.js (PM2 on GitHub). PM2 can run other scripts such as PHP, CoffeeScript and Ruby as well and it works on Linux, MacOSx and Windows.
You can install PM2 using npm (npm install pm2 -g). Make sure to add ¬†the -g to make a global install. Now you can simply start any Node.js app by running “pm2 start node_app.js”. “pm2 list” will show a list with running applications. Then you can generate a startup script¬†with “pm2 startup” to automatically start your apps on a computer reboot (which unfortunately doesn’t work on Windows, so I haven’t been able to test it). “pm2 monit” will show you some statistics on the current status of your applications.
Next to that PM2 has a deployment system, log management, a development tool (similar to nodemon which we’ve been using in this series), cluster mode (for running on multiple CPU’s, remember Node.js is single threaded)¬†and much more which you can all use as well.

There are some alternatives to PM2, such as forever, but something completely different is to run your Node.js app as a Windows service. You can do this by using NSSM (the Non-Sucking Service Manager) and winser. You can download NSSM from their website and you can install winser using npm (npm install winser). Then you should add the following lines to your package.json:

"scripts": {
    "postinstall": "winser -i -s -c",
    "preuninstall": "winser -r -x -s",
}

Now in the command prompt browse to the folder that contains the package.json and execute “node_modules.bin\winser -i”.¬†You have now installed your Node.js application as a service. To uninstall execute “node_modules.bin\winser -r”.

So I know that’s not much, but at least¬†these are some considerations when deploying a Node.js application.

HTTPS/SSL

You might want to deploy your application using HTTPS for secure SSL-encrypred traffic. For this you’re going to need some certificates, which I dont have.¬†Node.js has an https module, just like it has a http module. So now it shouldn’t be too difficult to write yourself an HTTPS enabled Node.js server.

var https = require('https');
var fs = require('fs');

var options = {
    key: fs.readFileSync('some-key.pem'),
    cert: fs.readFileSync('some-certificate.pem')
};

var server = https.createServer(options, function (req, res) {
    // Stuff...
});
server.listen(80, '127.0.0.1');

And here’s how you can use Express to handle HTTPS.

var app = require('express')();
var https = require('https');
var fs = require('fs');

var options = {
 key: fs.readFileSync('some-key.pem'),
 cert: fs.readFileSync('some-certificate.pem')
};

// Stuff...

var server = https.createServer(options, app`);
server.listen(80, '127.0.0.1');

And now you also know why you should use packages for your routing, you may want to re-use them.

MEAN alternatives

In this series we’ve seen the MEAN stack: MongoDB, Express, AngularJS and Node.js. It offers an alternative to the traditional LAMP stack, Linux, Apache, MySQL and PHP and the Microsoft stack with .NET¬†and IIS.¬†The baseline here is that we programmers just like to come up with cool or clever sounding acronyms. As I said before you can have a perfectly good MEN stack, leaving out the AngularJS. Or put in some Jade, or Sockets.io. Well, people have actually done that and came up with some other nice sounding acronyms. Here are some that I’ve seen: ANNE (AngularJS, Node.js, Neo4j, Express); BEANS (Bootstrap, Express, AngularJS, Node.js, Sockets.io); EARN (Express, AngularJS, Redis, Node.js). My point is that you’re not tied to MEAN, it’s simply a couple of technologies that work well together and can help you get things done.

If you like you can have a look at Sails.js, which is built on Express, but adds MVC and an ORM, among other things. Another alternative for Express (or Sails.js) is Hapi.js, which focuses more on configuration than code.

As alternative for MongoDB we’ve already seen Neo4j (a NoSQL graph database) and Redis (a NoSQL key-value store). They don’t actually have to be alternatives as you can use both in a single project. An actual alternative could be CouchDB, which is also a NoSQL document database and is probably the second most popular document database after MongoDB,
But who said you have to stick to NoSQL? If you’d like to use MySQL with Node.js that’s perfectly fine too!
If you just look at the Express database capabilities you’ll find databases such as Cassandra, PostgreSQL and ElasticSearch are supported out of the box.
And there are drivers for SQL Server and Oracle too.

Let’s look at some AngularJS alternatives. Of course there’s always jQuery that you can still use in your projects. Get some Knockout.js in your project too and you might not need AngularJS at all (although AngularJS is probably your first choice for SPAs (Single Page Applications).
While AngularJS is the most popular front end framework, it’s not your only choice. Underscore.js is another popular framework that is a little less bloated than AngularJS (but does less as well).
Another framework that you might want to try is Ember.js, which does pretty much everything that AngularJS does too. If you want to read more about Ember.js I can recommend Erik Hanchett’s blog.

And if you wish for another HTML template engine (or no template engine at all) you can ignore Jade and go with, for example, Mustache or Handlebars. Keep in mind you can use templating both on your back end and in your front end.

I’d mention alternatives for Node.js, but that would kind of defeat the purpose of MEAN and the (almost) all JavaScript stack. So let’s not do that (besides, you probably know them already).

Other popular modules

Let’s quickly check out some other popular Node.js modules. I’ll let you figure out how to use them on your own, but I’ll give a quick overview and a link to the website (with documentation).

The first library you might want to check is Browserify, which let’s you use require() in the browser. That’s pretty sweet!

Another popular library that you can use in both Node.js and in your front end is async. It provides many functions for asynchronous execution, such as each, map and filter on arrays.
It can also help you with asynchronous flow control. That is executing one task after another in an elegant and asynchronous manner. And for this same purpose the creator of async also gives us Nimble. And you might want to take a look at the alternatives Seq and Step as well.

So how about your minification, compilation, unit testing, linting (checking for syntax errors) etc.? For these tasks you can use Gulp or Grunt. Both applications are popular ‘task runners’ and can be easily installed using npm (using -g) and automate these kinds of tasks. They might take some configuration and some time to get¬†used to, but they’re worth it.

Last I’d like to point out commander. Since¬†everything nowadays seems to be working with the command prompt you might want to make your application command prompt configurable too. Something like “node server.js -super” where -super (or -s for short) starts your application in superman mode.¬†You don’t need a library for this, but it does come in handy. Commander seems to be the most popular one.

So that’s it for the entire MEAN series. I hope you’ve learned and enjoyed it as much as I have! This is the end of the MEAN series, but certainly not the end of my blogging career. In the future you may expect more posts on¬†web development, JavaScript, NoSQL, and who knows what. I’m always open for suggestions!

For additional reading on MEAN and related technologies I can once again recommend the Succinctly series by Syncfusion. They have many free ebooks like Node.js Succinctly, AngularJS Succinctly and MongoDB Succinctly. I’m also a big fan of the books by Manning Publications. Though not free they’re definitely worth your money. Books like Node.js In Action (second edition coming up), AngularJS In Action, MongoDB In Action (also a second edition coming up) and even Express In Action.¬†A book on the entire MEAN stack, Getting MEAN, is also in the writing (so get it early)!

I’ll be on a vacation in Poland for the next two weeks, so don’t expect a new blog post for at least another three weeks. Maybe a short one on a rainy day and if I have wi-fi in the hotel, but I’m not making any promises.

Thanks for sticking with me and happy coding!

MEAN web development #7: MongoDB and Mongoose

Last week we’ve seen some of the basic functionality of AngularJS, at least enough to get you started. Before that we’ve seen Node.js and Express. So that’s EAN and we’re left with the M. Well, Dial M for¬†MongoDB because that’s what we’re going to look at this week.

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

As usual you can find the examples for this post on my GitHub page in the mean7-blog repository.

Hello persistent data

I’ve already written an entire post¬†on NoSQL and MongoDB, A first look at NoSQL and MongoDB in particular. I’ve already told you to read it in the first part of this series, MEAN web development #1: MEAN, the what and why. If you haven’t read either of those I suggest you do so before continuing because I won’t repeat how to install MongoDB and MongoVUE. Don’t worry I’ll wait…

Before we continue I should mention that everything we’re going to do is async. That means lots of callback functions. We don’t want to block our main thread after all! It also means that the callbacks may not be called in the same order as their ‘parent functions’ are. Or that the records are actually inserted before we query them! Because I wanted to keep it simple in the complete example file I haven’t nested all examples in callbacks, but keep in mind that you may get some odd results. It worked fine for me by the way, if you get some weird results try running the examples one by one (simply commenting out the others).

So let’s just get a Node.js server up and running and write some data to the database real quick! You’ll be surprised how easy it is. First of all install the MongoDB driver using npm (npm install mongodb).
Next we’ll make a connection to our MongoDB instance.

var app = require('express')();
var MongoClient = require('mongodb').MongoClient;
     
var urlWithCreds = 'mongodb://user:password@localhost:27017/local';
var url = 'mongodb://localhost:27017/local';
MongoClient.connect(url, function (err, db) {
    if (err) {
        console.log(err);
    } else {
        console.log('Connected to the database.');
        db.close();
    }
});
var server = app.listen(80, '127.0.0.1');

So first of all we require Express (which isn’t necessary for MongoDB) and MongoDB. We take the MongoClient property of the MongoDB module. We use this client to connect to the database using the connect function, which takes a URI and a callback function. The callback has a MongoError (in case you can’t log in, for example if you have wrong credentials) and a Db as parameters.
We can use the Db object to do all kinds of stuff like creating and dropping databases, collections and indices and do our CRUD operations (Create, Read, Update, Delete). Let’s insert a simple object.

var url = 'mongodb://localhost:27017/local';
MongoClient.connect(url, function (err, db) {
    if (err) {
        console.log(err);
    } else {
        var artist = {
            name: 'Massive Attack',
            countryCode: 'GB'
        };
        var collection = db.collection('artists');
        collection.insertOne(artist);
        console.log(artist._id);
        db.close();
    }
});

As you can see we use the db parameter to get a collection (the MongoDB variant of a database table) using the collection function. If the collection does not exist it will create one automatically. We can then simply insert an object using the insertOne function of the collection. Now something funny has happened. After calling insertOne our artist object suddenly has an _id property. MongoDB uses this _id to uniquely identify objects.
So that wasn’t so bad right? Let’s look at other CRUD functionality!

CRUD with MongoDB

So let’s retrieve the record we just inserted. We can do this using the findOne function of the collection.

MongoClient.connect(url, function (err, db) {
    if (err) {
        console.log(err);
    } else {
        var collection = db.collection('artists');
        collection.findOne({ name: 'Massive Attack' }, function (err, artist) {
            if (err) {
                console.log(err);
            } else {
                console.log(artist);
            }
            db.close();
        });
    }
});

So the object that is passed to the findOne function is actually a search parameter. In this case we’re looking for documents (or records) that have a name equal to ‘Massive Attack’. The second parameter is a callback function that gives us an error, if any occurred, and the document that was retrieved. If you ran the previous example multiple times Massive Attack will be in your database more than once (having different values for _id), in this case findOne simply returns the first document it finds.

So let’s insert a few more artists, just so we’ve got a little set to work with. We can use the insertMany function for this.

collection.insertMany([
{
    name: 'The Beatles',
    countryCode: 'GB',
    members: [
        'John Lennon',
        'Paul McCartney',
        'George Harrison',
        'Ringo Starr'
    ]
},
{
    name: 'Justin Bieber',
    countryCode: 'No one wants him'
},
{
    name: 'Metallica',
    countryCode: 'USA'
},
{
    name: 'Lady Gaga',
    countryCode: 'USA'
}
], function (err, result) {
    if (err) {
        console.log(err);
    } else {
        console.log(result);
    }
});

Now you may think there’s a findMany function as well, but it’s actually just called find. find returns a Cursor which is something like an array, but not quite. We can use the toArray method though. The find function has a query parameter which is just an object that describes what fields of a document must have which values. We can search fields with AND, OR, NOT, IN, greater than, lesser than, regular expressions and everything you’re used to in SQL databases.

var findCallback = function (err, artists) {
    if (err) {
        console.log(err);
    } else {
        console.log('\n\nFound artists:');
        artists.forEach(function (a) {
            console.log(a);
        });
    }
};

// All documents.
collection.find().toArray(findCallback);

// Name not equal to Justin Bieber.
collection.find({ name: { $ne: 'Justin Bieber' } }).toArray(findCallback);

// Name equal to Massive Attach or name equal to The Beatles.
collection.find({ $or: [{ name: 'Massive Attack' }, { name: 'The Beatles' }] }).toArray(findCallback);

// Members contains John Lennon.
collection.find({ members: 'John Lennon' }).toArray(findCallback);

Now¬†let’s update a record.

collection.findOneAndUpdate({ name: 'Massive Attack' },
    { $set: {
        cds: [
            {
                title: 'Collected',
                year: 2006,
                label: {
                    name: 'Virgin'
                },
                comment: 'Best Of'
            },
            {
                title: 'Mezzanine',
                year: 1998,
                label: 'Virgin'
            },
            {
                title: 'No Protection: Massive Attack v Mad Professor',
                year: 1995,
                label: 'Circa Records',
                comment: 'Remixes'
            },
            {
                title: 'Protection',
                year: 1994,
                label: {
                    name: 'Circa'
                }
            }
        ]
        }
    }, function (err, result) {
    console.log('\n\nUpdated artist:');
    if (err) {
        console.log(err);
    } else {
        console.log(result);
    }
});

Here we see the findOneAndUpdate in action. Alternatively we could’ve used updateOne. And for¬†multiple updates we can¬†use¬†updateMany.

Now¬†let’s delete a record.¬†There’s one guy I really don’t want in my database (yes, I’ve added him so I wouldn’t feel guilty about deleting him). ¬†And for this we can, of course, use findOneAndDelete.

collection.findOneAndDelete({ name: 'Justin Bieber' }, function (err, result) {
    console.log('\n\nDeleted artist:');
    if (err) {
        console.log(err);
    } else {
        console.log(result);
    }
});

Really no surprises there. Alternatively there’s deleteOne and to delete many use, you guessed it, deleteMany.

Mongoose

So MongoDB with Node.js looks really good, right? It wasn’t very hard to use. It’s really just a matter of working with JavaScript objects. And as we all know JavaScript objects are very dynamic. In the previous examples we’ve already seen that¬†some artists have a member property defined and then when we updated we all of a sudden had a cds property and some CD’s¬†have a comment while others don’t… And MongoDB has no problem with it at all. We just save and fetch what is there.

Now try this.

var app = require('express')();
var MongoClient = require('mongodb').MongoClient;

var Artist = function (name, activeFrom, activeTo) {
    if (!(this instanceof Artist)) {
       return new Artist(name, activeFrom, activeTo);
    }
    var self = this;
    self.name = name;
    self.activeFrom = activeFrom;
    self.activeTo = activeTo;
    self.yearsActive = function () {
        if (self.activeTo) {
            return self.activeTo - self.activeFrom;
        } else {
            return new Date().getFullYear() - self.activeFrom;
        }
    };
};

var url = 'mongodb://localhost:27017/local';
MongoClient.connect(url, function (err, db) {
    if (err) {
        console.log(err);
    } else {
        var collection = db.collection('artists');
        // Empty the collection
        // so the next examples can be run more than once.
        collection.deleteMany();
        
        var massiveAttack = new Artist('Massive Attack', 1988);
        console.log('\n\n' + massiveAttack.name + ' has been active for ' + massiveAttack.yearsActive() +  ' years.');
        
        collection.insertOne(massiveAttack);
        
        collection.findOne({ name: massiveAttack.name }, function (err, result) {
            if (err) {
                console.log(err);
            } else {
                try {
                    console.log('\n\n' + result.name + ' has been active for ' + result.yearsActive() +  ' years.');
                } catch (ex) {
                    console.log(ex);
                }
            }
        });
        
    }
});

var server = app.listen(80, '127.0.0.1');

What happens is that MongoDB doesn’t store the yearsActive function nor the constructor function. What MongoDB stores are just the non-function values. The result is that when we retrieve our object it will no longer be an Artist object, but just an object that just so happens to have the same properties as an Artist.

This is where Mongoose comes to the rescue! Mongoose adds a schema to your MongoDB objects. Let’s see how that works.

To add Mongoose to your project you can install it using npm install mongoose.

So first we can use mongoose.connect to get a connection to the database.

var app = require('express')();
var mongoose = require('mongoose');

var url = 'mongodb://localhost:27017/local';
mongoose.connect(url);
var db = mongoose.connection;
db.on('error', function (err) {
    console.log(err);
});
db.once('open', function (callback) {
    // ...
});

var server = app.listen(80, '127.0.0.1');

After that we can define a schema using the Schema function.

db.once('open', function (callback) {
    var artistSchema = mongoose.Schema({
        name: String,
        activeFrom: Number,
        activeTo: Number
    });
    artistSchema.methods.yearsActive = function () {
        var self = this;
        if (self.activeTo) {
            return self.activeTo - self.activeFrom;
        } else {
            return new Date().getFullYear() - self.activeFrom;
        }
    };
});

And as you can see I’ve appended the yearsActive function to the artistSchema.methods object. After that we can create a¬†Model¬†using mongoose.model.

var Artist = mongoose.model('Artist', artistSchema);

And after that the Artist variable (a Model) is actually the portal to your collection. It’s also a constructor function for artists. So let’s create our Massive Attack artist.

var massiveAttack = new Artist({ name: 'Massive Attack', activeFrom: 1988 });
console.log('\n\n' + massiveAttack.name + ' has been active for ' + massiveAttack.yearsActive() + ' years.');

And then we can save it using the save function.

massiveAttack.save(function (err, result) {
    if (err) {
        console.log(err);
    } else {
        // ...
    }
});

And now that the artist is saved let’s retrieve it and call that yearsActive function again. We can simply retrieve our object using Model.findOne.

Artist.findOne({ name: massiveAttack.name }, function (err, result) {
    if (err) {
        console.log(err);
    } else {
        try {
            console.log('\n\n' + result.name + ' has been active for ' + result.yearsActive() +  ' years.');
        } catch (ex) {
            console.log(ex);
        }
    }
});

And here I’ve put the findOne directly in the callback function of save, which I didn’t do before. I needed this because calling findOne directly after save didn’t yield any results (timing issue I guess). More importantly it did successfully execute the yearsActive function!

And like with the regular MongoDB driver we can use find, remove, findOneAndRemove and findOneAndUpdate.

So we’ve looked at the MongoDB driver and at the problem of schemaless objects which Mongoose fixes. I can recommend practicing a bit, as it’s really very easy to drop, create, insert, update, read and remove data, and reading the API documentation of both. We’ve only scratched the surface here, but it got you on your way.

And of course I’m going to recommend some additional reading. The Node.js Succinctly book is just a great resource for Node.js in general and it has a tiny bit on MongoDB and SQLite as well. I can also recommend MongoDB Succinctly. And Getting MEAN from Manning even has a chapter on MongoDB and Mongoose.

Happy coding!

MEAN web development #6: AngularJS in the front

Hi all and welcome back! Welcome back to me too as I’ve been away for a while. Let’s just say I was enjoying¬†a summer vacation from blogging. But I’m back to finish this MEAN series! This week I’ve got AngularJS for you. Maybe next week too.
And in case you need a refresher, here are my previous posts about MEAN:

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

So in the previous post we’ve seen how we can build pages using the Jade template engine. Pretty sweet, but we need something bigger, better and badder for our front-end.

You can find the examples for this blog on my GitHub page in the mean6-blog repository.

What is AngularJS?

You may have heard of AngularJS before. It’s one of the most popular open-source front-end JavaScript frameworks for the web developed by Google. And, of course, it’s the A in MEAN. But what does it do?

AngularJS is an MVVM framework, much like Knockout.js.¬†It does a bit more than Knockout.js does though.¬†Next to bindings AngularJS can be used for DOM manipulation, more¬†like jQuery. And it does even more, like handling AJAX and routing. As Google likes to put it: AngularJS is¬†“Superheroic” in that it does just about everything.

So instead of talking let’s see some action! First of all we need to install AngularJS. You can download it from the AngularJS website, or you can install it through a package manager such as npm or Bower¬†(install angular). I’ve discussed all three methods in earlier posts so I will not repeat them here. Anyway, if you’ve downloaded my samples from GitHub you’ll be good to go.

The first examples of this post can be tested using nothing but the file system. For later examples with AJAX we’re going to need a little Node.js server, so I’ll add that later. The non-server examples can be found in the front-end.html and the front-end.js files.

So let’s take a look at a first example.

<html>
    <head>
        <meta charset="utf-8">
        <title>AngularJS example</title>
        <script src="node_modules/angular/angular.min.js"></script>
    </head>
    <body ng-app>
        <p>This is your first angular expression: {{ 'This is AngularJS' + ' syntax!' }}</p>
    </body>
</html>

So there are two things going on here. First is the ng-app directive in the body element. This tells AngularJS that body is the root element of our application and that AngularJS should do its magic. You can place it anywhere you want (like in the html element, or maybe a div element somewhere) and a page can have multple ng-app directives (which I won’t be doing in this post).

Next is, of course, the weird {{ }} syntax, which is the syntax AngularJS uses for its bindings. In this case you’ll see that ‘This is AngularJS’ and ‘ syntax!’ are, indeed, appended in your¬†browser, like it was just some JavaScript. Try using {{ 1 + 2 }} and you’ll see it will print ‘3’ since 1 + 2 equals 3 in JavaScript (and not ’12’).

Now let’s look at something really very cool. Suppose you want to bind some value to an input. Here’s how to do it.

<body ng-app>
    <p>Enter you name:
        <input type="text" ng-model="firstName" />
        <input type="text" ng-model="lastName" />
    </p>
    <p>You have entered: {{ firstName + ' ' + lastName }}</p>
</body>

No JavaScript required! Wow, that is so cool! And firstName and lastName are updated real time, while you’re typing! We bound our inputs using the ng-model directive¬†which takes care of creating and binding the firstName and lastName properties.

Enter controllers

You’ll often want more control over your code and putting all of your JavaScript into your HTML is not a good idea. So we’ll want to use AngularJS with some custom JavaScript file that we wrote. This is where¬†things get tricky. Not very tricky, but you just got to know how it works.

An AngularJS application is defined by modules. Modules then define controllers.

angular.module('fullNameApp', [])
    .controller('fullNameController', function ($scope) {
        $scope.firstName = '';
        $scope.lastName = '';
        $scope.fullName = function () {
            return $scope.firstName + ' ' + $scope.lastName;
        };
    });

So as we see here we create a module by calling the angular.module function and passing it more than one parameter. This returns an application so we can call the controller function directly on the return value. In the controller function we pass in the name of the controller, so we can use it in our HTML, and a constructor function, which receives a $scope variable to which we can append properties.

Now our HTML would look like this:

<html>
    <head>
        <meta charset="utf-8">
        <title>AngularJS example</title>
        <script src="node_modules/angular/angular.min.js"></script>
        <script src="front-end.js"></script>
    </head>
    <body ng-app="fullNameApp">
        <div ng-controller="fullNameController">
            <p>Enter you name:
                <input type="text" ng-model="firstName" />
                <input type="text" ng-model="lastName" />
            </p>
            <p>You have entered: {{ fullName() }}</p>
        </div>
    </body>
</html>

So as you can see we’ve now named our ng-app directive and we’ve added a div element with an ng-controller directive which points to our fullNameController controller. Finally, we now use the fullName function. Notice that we could now set default values in our controller and they’ll be displayed on our page automatically.

$scope.firstName = 'Sander';
$scope.lastName = 'Rossel';

More directives

So let’s take a look at some more directives that can help you build amazing pages. ng-repeat can be used to repeat an element for every item in a list. So let’s add a little array on our controller.

$scope.favoriteMovies = [
    'Star Wars',
    'Lord of the Rings',
    'Fight Club'
];

And display it in an unordered list.

<ul>
    <li ng-repeat="movie in favoriteMovies">
        {{ movie }}
    </li>
</ul>

Now we want to be able to add and delete items from the list. This next piece might blow your mind, but there’s a very simple directive to make a text input that can make a comma separated list and convert it to an array real time.

<input type="text" ng-model="favoriteMovies" ng-list />

So we bind the input to our favoriteMovies using ng-model and then use ng-list to convert it to a comma separated list. Try adding “, Pulp Fiction” (or whatever movie you like) to the text input and the movie will automatically be added to the unordered list we had before!
And if you want something else instead of a comma specifiy it in the ng-list, like so:

<input type="text" ng-model="favoriteMovies" ng-list=" | " />

And what if we add objects instead of strings?

$scope.favoriteAlbums = [
    { artist: 'The Beatles', title: "Sgt. Pepper's Lonely Hearts Club Band" },
    { artist: 'Moby', title: 'Play' },
    { artist: 'The Prodigy', title: 'Fat Of The Land' }
];
<ul>
    <li ng-repeat="album in favoriteAlbums">
        {{ album.artist + ' - ' + album.title }}
    </li>
</ul>

So how about making that editable?

<div ng-repeat="album in favoriteAlbums">
    <input type="text" ng-model="album.artist" />
    <input type="text" ng-model="album.title" />
</div>
<button ng-click="favoriteAlbums.push({})">New album</button>

And that’s where we see the ng-click in action. Of course we could’ve called a function on our controller too.

$scope.addAlbum = function () {
    $scope.favoriteAlbums.push({});
};
<button ng-click="addAlbum()">New album</button>

There’s a little problem with ng-repeat that isn’t quite obvious from these examples. ng-repeat creates a separate scope for each object in an array. For objects this is no problem, but if you were binding to an array of primitives, such as integers or strings, the values wouldn’t be updated.¬†So just remember to use objects when wanting to update array elements.

So how about adding a little styling to our page? With the ng-class directive we can add styles to elements based on some boolean value. The best part is you can add multiple classes based on one or more boolean values. So I have added a little embedded CSS to our page.

<style>
    .colored {
        color: red;
    }
 
    .underlined {
        text-decoration: underline;
    }
</style>

And two properties in the controller to specify whether we want some text to be colored and/or underlined.

$scope.addColor = true;
$scope.addUnderline = false;

Now in our HTML we can add two checkboxes for the two properties above and then add an ng-class directive on some element that adds the CSS classes based on the JavaScript properties.

Color: <input type="checkbox" ng-model="addColor" />
Underline: <input type="checkbox" ng-model="addUnderline" />
<p ng-class="{ colored: addColor, underlined: addUnderline }">This text might be colored and/or underlined!</p>

Pretty sweet, right? As you can see ng-class should simply evaluate to an object where each property is a class name with a value true or false to specify whether it should be applied.

But there’s an alternative. We could simply specify a string too. So consider the next JavaScript function which returns a string:

$scope.getClasses = function () {
    var classes = '';
    if ($scope.addColor) {
        classes += 'colored ';
    }
    if ($scope.addUnderline) {
        classes += 'underlined ';
    }
    return classes;
};

We can now use ng-class as follows:

<p ng-class="getClasses()">This text might be colored and/or underlined!</p>

Or you could return an array where each element is either an object such as in the first method or a string such as in the second method. I’ll leave that as practice for the reader though.

Also fun to mention, when you’re inside an ng-repeat directive you can use ng-class-even and ng-class-odd which work exactly as ng-class, but apply the styles only to even or odd elements.

Filters

AngularJS had a feature called filters. It can format values or actually filter lists.

Let’s go back to the first example. Let’s suppose you wanted to show full name in just uppercase or in just lowercase. This is an easy task!

<p>You have entered: {{ fullName() | uppercase }}</p>
<p>You have entered: {{ fullName() | lowercase }}</p>

We can also use a filter to format numbers and dates. It looks kind of the same, except this time you throw in a format.

<p>
    <input type="text" ng-model="number"><br>
    Number (default): {{ number | number }}<br>
    Number (no fractions): {{ number | number: 0 }}<br>
    Number (three fractions): {{ number | number: 2 }}
</p>
<p>
    Date (default): {{ date | date }}<br>
    Date (dd-MM-yyyy): {{ date | date: 'dd-MM-yyyy' }}<br>
    Date (yy/M/d): {{ date | date: 'yy/M/d' }}<br>
    Date (full): {{ date | date: 'fullDate' }}<br>
    Date (long): {{ date | date: 'longDate' }}
</p>

And for arrays you can do some awesome stuff too!  For this we use the orderBy or filter filter.

<h3>Ordered by title</h3>
<ul>
    <li ng-repeat="album in favoriteAlbums | orderBy: 'title'">
        {{ album.artist + ' - ' + album.title }}
    </li>
</ul>
<h3>Ordered by artist reverse</h3>
<ul>
    <li ng-repeat="album in favoriteAlbums | orderBy: 'artist' : true">
        {{ album.artist + ' - ' + album.title }}
    </li>
</ul>
<h3>Filtered on everything with '*y*'</h3>
<ul>
    <li ng-repeat="album in favoriteAlbums | filter: 'y'">
        {{ album.artist + ' - ' + album.title }}
    </li>
</ul>
<h3>Filtered on artist with '*y*'</h3>
<ul>
    <li ng-repeat="album in favoriteAlbums | filter: { artist: 'y' }">
        {{ album.artist + ' - ' + album.title }}
    </li>
</ul>

Keep in mind that we can get these values from our JavaScript controller as well. You can make the most awesome dynamic filters with¬†very little trouble. Just make sure you pass in an object with the same properties as the objects you’re repeating and set their values to the values you’d like to filter.

AJAX with AngularJS

So as mentioned AngularJS does a lot more than just HTML binding. One feature we’re going to look at here is that of the $http service. Needless to say we’ll need a little back-end server to communicate with, so for the AJAX examples I’m going to create a Node.js server and some new HTML and JavaScript so we can serve them up using our Node.js server.

Here’s the server:

var express = require('express');
var bodyParser = require('body-parser');
var app = express();

var books = [
    { title: 'Lord of the Rings', author: 'J.R.R. Tolkien' },
    { title: 'Harry Potter', author: 'J.K. Rowling' },
    { title: "The Hitchhiker's Guide to the Galaxy", author: 'Douglas Adams' }
];

app.use(bodyParser.json());
app.use(express.static('public'));

app.get(['/', '/index'], function (req, res) {
    res.sendFile(__dirname + '/public/ajax-example.html');
});

app.get('/books', function (req, res) {
    res.send(books);
});

app.post('/addBook', function (req, res) {
    var book = req.body;
    books.push(book);
    res.send(books);
});

var server = app.listen(80, '127.0.0.1');

So there’s a lot going on there. First of all I’ve added some Express. I’m also requiring body-parser (npm install body-parser), which is needed to get our POST data. Then I call the app.use function a couple of times. We’ve seen it before. It simply adds a middleware to a path. In this case we tell it to parse any JSON body so we can use it in our app. We also tell it that we can serve static files from the public folder (so we can serve the HTML and JavaScript file).
After that we serve the page by browsing to the root¬†or root/index. I’ve also specified a GET for root/books, which simply returns a list of books (as JSON). And, what it’s all about, a POST to add a book to the list of books.

Let’s look at our front-end JavaScript.

angular.module('ajaxApp', [])
    .controller('ajaxController', function ($scope, $http) {
        $scope.newAuthor = null;
        $scope.newTitle = null;
        $scope.books = [];
        $scope.getBooks = function () {
            $http.get('http://localhost/books')
            .then(function (response) {
                $scope.books = response.data;
            }, function (response) {
                alert('Something went wrong while getting the books!');
            });
        };
    $scope.addBook = function () {
        $http.post('http://localhost/addBook', { author: $scope.newAuthor, title: $scope.newTitle })
            .then(function (response) {
                $scope.newAuthor = null;
                $scope.newTitle = null;
                $scope.books = response.data;
            }, function (response) {
                alert('Something went wrong while adding a new book!');
            });
        };
    });

So that’s quite a thing too!¬†First of all notice a $http parameter being passed to the controller constructor function. We’ll need this $http parameter to make HTTP calls. Now we first use this in the getBooks function. You’ll see that using this $http stuff is actually very simple! We use $http.get and pass it our URL to get the books. It returns a promise, which has a then function that takes two callbacks, a success function and a failure function. The functions are executed once the asynchronous call returns (AJAX is asynchronous, remember?). So if everything goes right we simply assign the data (a list of books) to the books property. If something goes wrong we show an alert.

In the addBook function I’m using the $http.post function. It’s really similar to the get example, except we’re now passing in some data, a new book. Upon success the book list, including the new book, is returned and we reset the newAuthor and newTitle (nice example of two-way binding by the way).

Now for the HTML:

<html>
    <head>
        <meta charset="utf-8">
        <title>AngularJS AJAX example</title>
        <script src="angular.min.js"></script>
        <script src="ajax-example.js"></script>
    </head>
    <body ng-app="ajaxApp">
        <div ng-controller="ajaxController">
 
            <h2>AJAX example</h2>
            <button ng-click="getBooks()">Get books</button>
            <ul>
                <li ng-repeat="book in books">
                    {{ book.author + ' - ' + book.title }}
                </li>
            </ul>
 
            <input type="text" ng-model="newAuthor" />
            <input type="text" ng-model="newTitle" />
            <button ng-click="addBook()">Add book</button>
        </div>
    </body>
</html>

And there you have it!

So AngularJS can do two-way binding, supports MVVM and MVC architecture, it can do AJAX, but also routing, internationalization and localization, you can write custom directives and customize all you like, it supports testing and it has lots of directives I haven’t discussed like ng-show, ng-hide, ng-form, ng-blur… I guess Google wasn’t exaggerating when they called AngularJS ‘superheroic’ because it really seems to have some super powers!

And of course I’ll be leaving you with some recommended reading.¬†As you know I’m a big fan of the (free) Succinctly series by Syncfusion, so here’s two must reads: AngularJS Succinctly and Node.js Succinctly. Also check out these awesome books by Manning Publications: AngularJS In Action, AngularJS In Depth, Node.js In Action (Second Edition) and Getting MEAN. And a book I’ve recently picked up at work: Pro AngularJS.
Well, that should keep you busy for a few months!

Happy coding!

MEAN web development #5: Jade and Express

In the last few weeks it was my time to shine… In absence. Been quite busy with, you know, stuff. But here I am ready to give you a new installment of the MEAN web development series! If you haven’t read my previous posts, or if you’ve forgotten all about them in my absence, you can find them here:

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

So in my previous blog from a few weeks back I’ve talked about using Express in Node.js. One thing I haven’t discussed yet is the templating option of Express. As that is actually quite simple this blog will be more about the template engine Jade than about Express. Of course we’ll use both to build a few pages.

You can find the examples for this blog on my GitHub page in the mean5-blog repository.

Starting out with Jade

So you can probably guess our first step (assuming you’ve already installed Node.js)… If it included npm somehow you are correct. We need to install Jade using npm. We’ll also want Express, of course, you know how it goes! You can read about npm and how to use it in my first MEAN article, MEAN web development #1: MEAN, the what and why. So create a folder for your project somewhere, optionally create a package.json file (containing at least an opening and closing bracket), open up a command prompt¬†and use the following commands.

cd C:\project-folder
npm install express --save
npm install jade --save

The –save is optional and only makes sense when you created a package.json file.

Finally create your server.js file where your actual JavaScript goes. So now you have everything you need to start using Node.js, Express and Jade.

Let’s not do that yet though. Let’s take a step back. What exactly is Jade and why would you want to use it? Jade is a template engine, which means you can write some pseudo-HTML which the Jade engine can transform into actual HTML. One reason to use Jade is because it saves typing, “h1 Examples” will output “<h1>Example</h1>” for example. So that saves like seven characters, but it adds up.
Less typing is the least good reason to start using Jade though. When using Jade it is possible to pass some JavaScript object to your Jade code and build your page differently depending on your JavaScript. For example you might have an array and you want to iterate over the array to show a table on your page. Or maybe you just want to show the name of the logged in user in the top right corner.
Jade also supports and encourages a more object oriented style of writing your HTML. That’s awesome because you can now write a piece of HTML¬†Jade once and use it everywhere.

Sounds good, right? But isn’t all of this already possible using PHP, Java or C#? Yeah, sure. And you can even do this in Node.js. Simply create a string containing your HTML, do some string concatenation, replaces, etc. No problem at all.
So why would you still want to use Jade? Because Jade makes it easy! All the string concatenation and replaces you’d have to do in PHP or “vanilla” Node.js is done for you. What’s left is a file that’s easier to read than the HTML it ultimately produces! And the good thing about Jade is that it has Node.js and Express support out-of-the-box!

Hello Jade!

I think that title says it all, no? We won’t be using Node.js and Express just yet though. In fact I want you to fire up a command prompt and install Jade again, this time globally so we can use it from the command prompt.

npm install jade -g

Now create¬†a folder in the Node.js project we just created and call it jade-examples. We’re going to use this folder and some of the examples later with Node.js and Express. So in that folder create a file and call it hello-jade.jade.¬†If you got my sources from GitHub you can find the file in jade-examples. Put the following code in the file.

html
  head
    title Hello, Jade!
  body
    h1 Hello, Jade!
    p This is awesome!

So that’s maybe a bit much for a simple Hello World example, but I’m pretty sure you can figure out what HTML this will generate. One thing I’d like to point out is that Jade is whitespace sensitive.¬†More specifically, you must¬†use whitespaces to nest elements. That means that you got to be really careful with your spaces, they’re not just makeup!
I recently spent an evening debugging some Haskell code (which is also whitespace sensitive) because I had used spaces on one line and a tab on another. Try figuring that out, it all looks the same!
I recommend using spaces by the way, if your editor supports it look for the option that converts tabs to spaces and you’ll be safe.

So how to get some HTML out of this? With the command prompt, of course. So browse to the folder where you’ve put your file and use the following command.

cd file-folder
jade hello-jade.jade

Now check it out, it generated a hello-jade.html file. It’s not very readable though. Everything is put on a single line! Let’s fix that. You can use some options in the command prompt. We’re going to use -P (that’s a capital P).

jade hello-jade.jade -P

Looks a look better, doesn’t it?

<html>
  <head>
    <title>Hello, Jade!</title>
  </head>
  <body>
    <h1>Hello, Jade!</h1>
    <p>This is awesome!</p>
  </body>
</html>

For multiline text you should use one of the following methods. Use a dot after your element or use pipes | on every single line.

p.
  This is one line.
  This is a second.
p
  |This is one line.
  |This is a second.
p
  This won't work.
  It just won't.

The HTML that is generated looks as follows.

<p>
  This is one line.
  This is a second.
</p>
<p>
  This is one line.
  This is a second.
</p>
<p>
  <This>won't work.</This>
  <It>just won't.</It>
</p>

As you can see Jade will happily generate syntactically correct, yet invalid HTML! Keep in mind that HTML isn’t whitespace sensitive so the above HTML will still render the two lines of text on a single line in your browser. If you need a seperate line you’ll have to insert a <br> element.

Doing more with Jade

So now that we’ve got that out of the way let’s look at some other features of Jade. Of course you can add attributes to your elements.

h1(id="header") Attributes
p(class="text") This is an example using attributes.
p Here's a text input.
input(type="text")

I won’t show you the HTML output as you can generate it yourself or look at the files from my GitHub.

Here’s some other stuff we can do with Jade.

// This comment will be visible in our HTML.
//- This one won't (it's the hyphen!)
//- Ids are so common we have a shorthand!
h1#header Attributes
//- Same goes for classes.
p.text This is an example using attributes.
p.text.second-class.third-class Here's a text input.
input(type="text")
//
  Block comment
  With lots of space
  And lines

p Some text with another <strong>element</strong>.

//-
  Yes, this is possible,
  but we need to put it on a new line
  and prefix it with a pipe.
| Some text without enclosing tags.

Using JavaScript

So that’s all pretty cool, but you probably want more. You’re in luck, because there’s much more! In fact, you can use JavaScript to generate HTML. That means you can have any JavaScript object and use it just like that.

For the next example we’re going to need two files. First is our Jade file. I’ve called it javascript.jade.

h1= title
p= text

The = sign means some code will follow. So “title” and “text” is actually code. More precise they’re properties/variables. Using = will also filter your JavaScript to prevent injection attacks. If you like to disable this feature simply use != instead.

You could generate HTML from the above Jade file, but since title and text are not set you’ll just get an empty header and paragraph. So we’ll need to pass in something to the engine so it knows how to interpret those values. We can do that using a JSON file. So create another file, I’ve called it javascript.json, and put in the following JSON.

{
  "title": "Jade and JavaScript!",
  "text": "You can just insert JavaScript Objects into your templates!"
}

Now we can use the command prompt to generate the HTML using the JSON file. Notice that we’ll use a capital O in the next sample.

jade -O javascript.json javascript.jade

This will generate the HTML and it will have replaced title and text with the values from your JSON file. Awesome!

In the next example I’ve included all JavaScript into the Jade file so we don’t need a seperate JSON file. Try setting the showHeader variable to false and generate the HTML again. Also notice the difference between the escaped and the unescaped code.

//-
  The following code
  will not be shown
  in your HTML.
  We'll use - instead of =

-
  var showHeader = true;
  var header = 'Jade is awesome!'

//- Single line code.
- if (showHeader)
  h1= header

//- Native Jade syntax!
if showHeader
  h1= header

//- Multiline code.
-
  var movies = [];
  movies.push('Star Wars');
  movies.push('Lord of the Rings');
  movies.push('Harry Potter');

ol
  each movie in movies
    li= movie

- var code = 'HTML may look like this: <p>Hello, Jade!</p>';
//- Some escaped code.
p= code
//- Some unescaped code.
p!= code

Inheritance

So how about we look into that inheritance now? Most, if not all, websites have a standard structure that’s the same across the entire page. We have a header at the top, footer at the bottom, a menu on the left, top or right and the content in the middle. And it’s usually the middle part that changes while the rest stays more or less the same. So let’s define that basic layout. I’m going to keep it simple so I’ll just have a page with a fixed footer. For simplicity I’m just going to use embedded CSS in our Jade template. I’ve called the following file base.jade.

html
  head
    style(type="text/css").
      html {
        position: relative;
        min-height: 100%;
      }

      body {
        margin: 0 0 100px;
      }
 
      footer {
        background-color: #41a62a;
        position: absolute;
        left: 0;
        bottom: 0;
        height: 100px;
        width: 100%;
      }
    block head
  body
    div#content
      p This is the content!
      block content
    footer
      p This is the footer!
      block footer

This looks a lot like what we already know. The only weird thing here are those blocks.¬†The block elements aren’t visible in the generated HTML, so it’s completely possible to use a ‘base’ page as a regular page on your site.
Now those blocks can be overridden by inheritors. So block content can be replaced with anything you like. Let’s see what that looks like. I’ve created an base-inheritor.jade file which extends base.jade.

extends base.jade

block head
  title Inheritor

block content
  p This is the inheritor page!

block footer
  a(href="#") Some link

The file starts with extending base.jade (that’s actually the relative path to the file, since I have it in the same folder it’s just the file name). After that I’m filling in the content for each block. It’s totally optional to override a block.
Now you can simply generate the HTML for base-inheritor.jade and you’ll see the entire base¬†is generated too!

There’s a little more you can do with those blocks though. Here’s a simple file called blocks.jade.

block header
 h1 Inheritance using Jade!

block content
 p Here is some content.

block footer
 p This is the footer.

As you can see I’ve put some content in each of those blocks. In an inheritor we can replace that content, append to that content or prepend to that content. This is illustrated in blocks-inheritor.jade.

extends blocks.jade

block header
  h1 Another header!

prepend content
  p This is even more content!

append footer
  a(href="#") Some link

You may use “block append” or “block prepend”, but¬†the block keyword is¬†optional. Now generate the HTML and check out the results!

It’s also possible to put blocks in blocks, but I’ll leave that as practice for the reader.

Mixins

Now there is one last feature I’d like to show you, which is mixins. A mixin is a bit like a function, a reusable piece of Jade! Let’s just look at some examples.

//- Here is a mixin.
mixin lorem
  h2 First paragraph of Lorem Ipsum...
  p Lorem ipsum [...]

h1 Mixins
//- Mixin usage is a big plus!
+lorem
+lorem
+lorem

h2 Animals
- var animals = ['Cat', 'Dog', 'Goldfish'];

//- A mixin with a parameter and JavaScript!
mixin isKnownAnimal(animal)
  if animals.indexOf(animal) >= 0
    p= 'The ' + animal + ' is a known animal.'
  else
    p= 'The ' + animal + ' is not a known animal!'

+isKnownAnimal('Cat')
+isKnownAnimal('Dog')
+isKnownAnimal('Parrot')

Pretty awesome, right?

Express

So that’s all the Jade I’ve got for you! You can now create Jade pages and generate HTML through the command prompt. We’d use it within Node.js though! So the time has come to get back to the project we created at the start of this post.

In the server.js you need to do two things. Tell Express where to find its templates and what engine to use when rendering those templates. Then on a request render any template you like.
It’s that easy!

Now we’ve got all these Jade examples¬†we can generate using Express! I picked a few interesting ones. Here’s the code for the entire server.js.

var express = require('express');
var app = express();

app.set('views', './jade-examples')
app.set('view engine', 'jade');

// Use hello-jade as index.
app.get('/', function (req, res) {
    res.render('hello-jade');
});

app.get('/javascript', function (req, res) {
    res.render('javascript', {
        title: 'Jade and JavaScript!',
        text: 'You can just insert JavaScript Objects into your templates!'
    });
});

app.get('/base-inheritor', function (req, res) {
    res.render('base-inheritor');
});

app.get('/mixins', function (req, res) {
    res.render('mixins');
});

var server = app.listen(80, '127.0.0.1');

Is that all? That’s all!

So I usually give you some reading recommendations at the end of a blog, but I really haven’t got anything for Jade. You can get a lot from the language reference on the Jade website, although it’s hardly a good place to start.
Of course you can always check out some books by Manning, like Express.js in Action, which has a chapter on templating in Express and Jade. And keep an eye out for the ebooks by Syncfusion. Node.js Succinctly has a chapter on Express and JavaScript Succinctly is always handy when working with JavaScript.

Hope to see you again next week.
Stay tuned!

MEAN web development #4: All aboard the Node.js Express!

Hi everyone. After my little excursion to Polymer we’re back at MEAN web development! In my previous MEAN post about Node.js I asked you what you wanted to read next, Express or MongoDB. I got a request for Express, so that’s what this post will be about. Don’t worry, we’ll get to MongoDB later. If you’re not up and running yet you can check out my previous posts.

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

The code examples for this post are, as usual, on my GitHub account in the mean4-blog repository.

Also be sure to follow me on Twitter @sanderrossel for industry updates and more blogs on MEAN, Node.js, Express, MongoDB, AngularJS and related technologies.

Express

Express is a pretty generic framework for Node.js, or a minimal and flexible Node.js web application framework as they put it.
Node.js is pretty bare bones and has only the most basic server functionality. That’s a good thing because that means other people, like the Express team, can do things their way. And so Express just handles a lot of the low level work for you. Parsing paths and queries, check; routing, check; templating, check. So it’s no wonder that Express is a pretty popular Node.js framework! There are some alternatives for Express, like¬†Koa and Hapi, but I won’t discuss those here.

I have already explained how to install Node.js and add Express to your project in MEAN web development #1: MEAN, the what and why and we’ve used some Express in MEAN web development #2: Node.js in the back. So if you haven’t read those articles yet I suggest you read them now. Don’t forget about nodemon either, a very nice tool¬†for testing Node.js applications!

Starting from this post I’m also just going to host our sites on port 80 (instead of 1337). This has the advantage that we can just visit localhost instead of localhost:portNumber because 80 is the default HTTP port. That said, other applications might use port 80 (like SQL Server Management Studio Reporting Services). If port 80 isn’t working for you simply use another port (or make port 80 available by closing the application that’s using it).

Routing

In MEAN web development #2: Node.js in the back we’ve already seen some routing examples. Let’s go over that again real quick and see some other really nice routing features of Express.js!

So let’s say you have a very simple website with a homepage and an about page. Your Node.js Express server JavaScript file may look a bit like this.

var express = require('express');
var app = express();

app.get(['/', '/index'], function(req, res) {
    res.send('This is the homepage!');
});

app.get('/about', function(req, res) {
    res.send('This is the about page!');
});

var server = app.listen(80, '127.0.0.1');

That’s cool, but what if you wanted to log every request you got? Sure, you could create a function and call it in both handlers, but if you get a lot of handlers that will become a little tiresome. Especially when you’re going to move your routing to external files. And after you’ve added the logging you want to implement some login handler and some blacklist checker and… Well you get the point.
What I haven’t told you yet is that you can chain request handlers so you can reuse them. Let’s check that out. For your homepage it may look like this.

var express = require('express');
var app = express();

app.get(['/', '/index'], function(req, res, next) {
        console.log(req.originalUrl + ' requested @ ' + new Date().toISOString());
        next();
    }, function(req, res) {
        res.send('This is the homepage.');
});

var server = app.listen(80, '127.0.0.1');

By specifying the next parameter in the first callback function and executing it the next handler will be called. Failing to either call next() or res.send()¬†will make your website very unresponsive (it just freezes, so don’t forget). So here we get a logging of each request to our homepage.

And now we can easily refactor that and implement it for the about page too.

var express = require('express');
var app = express();

var logger = function(req, res, next) {
    console.log(req.originalUrl + ' requested @ ' + new Date().toISOString());
    next();
};

app.get(['/', '/index'], logger, function(req, res) {
    res.send('This is the homepage.');
});

app.get('/about', logger, function(req, res) {
    res.send('This is the about page.');
});

var server = app.listen(80, '127.0.0.1');

Now let’s add a blacklisted handler to our site. Usually you would have some list of blacklisted IP addresses and reject them access, but since we’re testing from localhost I’m just going to check for a blacklisted query parameter. Notice that the blacklisted function either calls res.send() or next(). We can pass in an array of handlers to app.get(), so that makes our lives a little easier.

var express = require('express');
var app = express();

var logger = function(req, res, next) {
    console.log(req.originalUrl + ' requested @ ' + new Date().toISOString());
    next();
};

var blacklisted = function(req, res, next) {
    if (req.query.blacklisted == 'true') {
        res.send('You are blacklisted on this site!');
    } else {
        next();
    };
};

var globalReqHandlers = [logger, blacklisted];

app.get(['/', '/index'], globalReqHandlers, function(req, res) {
    res.send('This is the homepage.');
});

app.get('/about', globalReqHandlers, function(req, res) {
    res.send('This is the about page.');
});

var server = app.listen(80, '127.0.0.1');

You can get ‘blacklisted’ by adding “?blacklisted=true” to the end of your URL, for example “localhost/about?blacklisted=true”. So that’s pretty cool! But it gets better. We can use app.use(). This will append some request handlers (also called middleware) to the routings. Be sure you add your handlers in the correct order as they’re executed in the same order you added them. So this would look as follows.

var globalReqHandlers = [logger, blacklisted];

app.use('/', globalReqHandlers);

app.get(['/', '/index'], function(req, res) {
    res.send('This is the homepage.');
});

app.get('/about', function(req, res) {
    res.send('This is the about page.');
});

Notice that the listener for the homepage and the about page no longer have the globalReqHandlers specified, but the requests will still be logged.

So let’s add a little admin panel. Whenever someone accesses the admin panel we want to make sure this user is an admin. How would this go?

app.use('/', globalReqHandlers);
app.use('/admin', function(req, res, next) {
    if (req.query.admin == 'true') {
        next();
    } else {
        res.send('You are not an admin on this site!');
    };
});

/* Homepage and about... */

app.get('/admin', function(req, res) {
    res.send('This is the admin panel.');
});

app.get('/admin/users', function(req, res) {
    res.send('This is the admin users page.');
});

Whenever you now¬†try to access an admin page you need to be an admin (by adding “?admin=true” at the end of your URL). Notice that a request for an admin page still gets logged and checked for the blacklist. The homepage and about page, however, don’t check if the user is an admin.

So you can imagine this stuff clutters up your server file pretty quickly. Let’s move these routing handlers to separate files. If you’re unfamiliar with modules in Node.js I suggest you read my previous MEAN article, MEAN web development #3: More Node.js.

So create two files in node_modules, called routing.js and routingAdmin.js.

Here is the code for routing.js.

var express = require('express');
var router = express.Router();

var logger = function(req, res, next) {
    console.log(req.originalUrl + ' requested @ ' + new Date().toISOString());
    next();
};

var blacklisted = function(req, res, next) {
    if (req.query.blacklisted == 'true') {
        res.send('You are blacklisted on this site!');
    } else {
        next();
    };
};

var globalReqHandlers = [logger, blacklisted];

router.use('/', globalReqHandlers);

router.get(['/', '/index'], function(req, res) {
    res.send('This is the homepage.');
});

router.get('/about', function(req, res) {
    res.send('This is the about page.');
});

module.exports = router;

And here’s the code for adminRouting.js.

var express = require('express');
var router = express.Router();

router.use('/', function(req, res, next) {
    if (req.query.admin == 'true') {
        next();
    } else {
        res.send('You are not an admin on this site!');
    };
});

router.get('/', function(req, res) {
    res.send('This is the admin panel.');
});

router.get('/users', function(req, res) {
    res.send('This is the admin users page.');
});

module.exports = router;

So we’re using the Express.Router object and do much the same to it as we did with app earlier. Do notice that I’m just mapping to ‘/’ and ‘/users’ in the adminRouter though. In our server file we can now use these modules¬†as follows.

var express = require('express');
var routing = require('routing');
var adminRouting = require('adminRouting');
var app = express();

app.use('/', routing);
app.use('/admin', adminRouting);

var server = app.listen(80, '127.0.0.1');

So as you can see I can now use and reuse the routing! And it is here that I map the admin routings to /admin. So how cool is that? I thought so too!

There’s one last thing I’d like to show you. I won’t implement it, but I thought you’d like to know it’s there since it’s pretty cool! You can use app.route() to chain HTTP¬†methods¬†to a request. So far we’ve only seen GET (app.get()), but app has a method for each HTTP method (app.post(), app.put(), app.delete()…).

app.route('/admin/users')
    .get(function(req, res, next) {
        // Handle GET here...
    })
    .post(function(req, res, next) {
        // Handle POST here...
    }) // etc.
);

404

So now that we have all of our routing in place we can define a handler for the well known 404! So if all else fails, and a request couldn’t be handled, we return this. Luckily that’s really very easy.

app.use('*', function(req, res) {
    res.status(404).send("Well, looks like we've got a four-o-four, boys! (That mean the page was not found)");
});

We simply hook up another middleware! The ‘*’ is a wildcard character and means it responds to anything we throw at it. For this reason it’s very important to put the 404 handler after all your other handlers! Remember that your handlers are executed in the order you add them to your app, so if this one is added before anything else this will handle the request¬†and anything¬†after this will be ignored. Notice I’m setting the status to 404, which is the HTTP status¬†code for “Not Found” and let’s the browser know the page couldn’t be found. You can set any status using Response.status(), but usually you won’t have to. Other status codes include 200, OK (the default); 202, Accepted; 400, Bad Request; 403, Forbidden and 500, Bad Request (and there’s lots more).

I’d like to focus on the wildcard for a bit. There are a few patterns you can match, including any Regular Expression.
* means just any character(s). So ‘/sander‘ would match ‘sanderrossel’, but also ‘sanderexpress’ or just ‘sander’. ‘/sanderss*’ would match ‘sanderrossel’ and ‘sanderexpress’, but not ‘sandernodejs’.
A character may appear more than once. You can use a plus symbol, for example ‘/go+gle’ (coun’t the amount of zeroes and navigate to that page in the search results?). Of course it matches ‘gogle’, ‘google’, ‘gooogle’ and so on.
You can also mix in optional characters using the questionmark. For example ‘/express?’ would match ‘express’ and ‘expres’.
You can group characters using parenthesis. ‘/express(js)?’ matches ‘express’ and ‘expressjs’, but not ‘expressj’.
Why would you use this? You can now write a single handler for ‘page’, ‘page.htm’, ‘page.html’, etc. That’s pretty neat!

You can play around with it by adding the following middleware to your server (before the 404) and browsing to localhost/yourpatternhere (or ‘yourcoolpattttern’, ‘yourpatternhere’ or ‘yourawesomepattttternhere’, but not ‘yourpatter’ or ‘yourpaternhere’).

app.get('/your*patt+ern(here)?', function(req, res) {
    res.send('Matched the pattern!');
});

Error handling

So what happens when something goes wrong? Perhaps your connection to the database failed when looking up that blacklist. Luckily adding some error handling isn’t difficult. Just add another middleware! The error handler needs to have four parameters passed to it, whether you use them or not. That way Express knows it’s an error handler.

app.use('/', function(err, req, res, next) {
    console.error(err.stack);
    res.status(500).send('Oops, looks like you broke something!');
});

You need to add that even after your 404, after all 404-ing may cause an error! So now we only need to have an error to test this. You can add the following code (before the 404!) and browse to localhost/error.

app.get('/error', function(req, res) {
    // something is undefined.
    var error = 1 / something;
    res.send('Code will never come here.');
});

Of course you can add specific error handlers for specific pages. Simply change the path of your handler. For example, the following code will only handle any errors on admin pages.

app.use('/admin', function(err, req, res, next) {
    console.error(err.stack);
    res.status(500).send("Oops, looks like you broke something! That's not very admin-ish of you!");
});

Do notice I’m setting the status to 500. You can use the error object for information about the error.

And of course you can chain error handlers. Keep in mind that only the first handler needs the err parameter!

var logger = function(err, req, res, next) {
    console.error(err.stack);
    next();
};

var dbLogger = function(req, res, next) {
    console.log('Error logged to DB.');
    next();
};

var serveErrPage = function(req, res, next) {
    res.status(500).send('Oops, looks like you broke something!');
};

app.use('/', logger, dbLogger, serveErrPage);

And what happens if even your error handling fails? Guess you better set up a safety net.

app.use('/', logger, dbLogger, serveErrPage);
app.use('/', function(err, req, res, next) {
    // Everything failed...
    res.status(500).send('Even the error handling is bugged...');
});

And we can generate an optional error by, you guessed it, passing it in as a query parameter. Let’s handle it in the logger function.

var logger = function(err, req, res, next) {
    if (req.query.err == 'true') {
        var error = 1 / somethingElse;
    };
    console.error(err.stack);
    next();
};

So localhost/error for the regular error handling. localhost/error?err=true to generate an error in the error handling.

Of course you could’ve put the error handlers in the routing file too! I won’t do that, but just know that it’s an option.

One last thing. The app.get(), app.use() etc. all have a path parameter, it’s the ‘/’, ‘/admin’¬†parameter.¬†It’s optional. I’ve specified it every time for clarity, but you may omit it and it will default to ‘/’.
So app.use(‘/’, handler) is the same thing as app.use(handler).

In this post we’ve taken a good deep look at the routing functionality of Express. As you can see it’s all pretty easy. There’s more you can do with Express, especially when you install some third-party middleware, like cookie-parser, cookie-session, express-session or compression.
There’s an¬†important feature of Express that we haven’t seen yet, which is templating. You can use template engines, like Jade¬†or Mustache, with Node.js and Express. We’ll use Express and Jade in a later post!

And, as usual, I’m going to recommend some books. First there’s the Succinctly ebooks by Syncfusion that I keep recommending because they’re great and they’re free. If you feel you’re still not up to speed, or looking to get up to speed, with Node.js and Express take a look at JavaScript Succinctly, Node.js Succinctly and HTTP Succinctly.
I can also recommend the books by Manning Publications. They have some good stuff on Node.js and Express!

Stay tuned!

MEAN web development #3: More Node.js

Welcome back! In my last post we’ve looked at Node.js and added in some Express. You might think that’s that for Node.js, but actually there is just more Node.js stuff I’d like to talk about. So what do I have in store for you this week? We’ll be looking at modules and events, two important aspects of Node.js.

If you haven’t read my previous articles on MEAN and Node.js yet I strongly advice to read them now as this post continues where the previous one left off (although we won’t be using Express in this post).

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

As always you can find the sources for this blog on my GitHub account in the mean3-blog repository.

And be sure to follow me on Twitter @sanderrossel for more content related to MEAN, Node.js, web development and software development in general.

Modules

In my previous post you’ve already had a brief introduction to modules. Every time you use a require(‘http’) you’re loading the http module. There’s lots of modules, like http, https, net (for socket programming), mongodb, express and just a whole lot more (thousands!). Some come with Node.js, like http, and some need to be¬†added, either manually or through a package manager like npm, like mongodb (which we’ll use in the ‘M post’ of this series!).

Why would you want to create modules? Think of it as a package, a piece of code that is reusable across files and projects. Let’s say you write an awesome bit of code, or just some code you need a lot. You can put this in a module¬†and use it everywhere you like. You can even distribute it (to GitHub, npm, Bower…) so others can use it too!

So let’s build a module. You won’t believe how easy it is! Create a file, myModule.js, and place it in the same folder as your Node.js application. Now in myModule.js simply put the following JavaScript.

exports.hello = "Hello, module!";

Now in your main Node.js application you can use it as follows.

var myModule = require('./myModule.js');
console.log(myModule.hello);

Can you believe it’s that easy!? I’m not entirely happy though. I’m requiring a file in a location. The ./ indicates the folder in which the¬†Node.js file that did the require is located. When we call http, a native module, we don’t need to specify a path though. Alright, but that’s native you might say. But when requiring Express, as we’ve done in my previous post, we didn’t need to specify a path either! Well here’s the thing, when you don’t specify a path Node.js will look for a file with the specified name in the node_modules folder. So if it doesn’t already exist create a folder with the name node_modules and put your myModule.js in it. You can now load it using the following syntax.

var myModule = require('myModule');

That looks better! However, if you’ve installed Express you’ll see that Express has a folder inside the node_modules folder with other¬†folders and¬†files in it. That’s what I want too! Luckily that’s not hard to do either. First we create a folder inside node_modules called myModule. Then we can either create a package.json and put the following JSON in it.

{ "name" : "myModule",
  "main" : "./node_modules/myModule/myModule.js" }

Or we can rename myModule.js to index.js and require will try to get the index.js (or index.node) from node_modules/parameter_passed_to_require/index.js.

So let’s sum that up real quick. Require tries to get the file you passed in as a parameter or, if you didn’t specify the path, it will try to load ./node_modules/parameter_passed_to_require.js or¬†./node_modules/parameter_passed_to_require/index.js where ./ is the folder of the file that does the require.

Exports

So we can now create the simplest of module and load it using require. But we don’t really understand what’s going on yet. Where did this ‘exports’ thing come from and how can we utilize it?

When using require to get a module require will actually provide you with the exports variable. It’s shorthand for module.exports, so you may use that too. require will simply return the exports object. Basically, when writing a module, imagine the following lines of JavaScript at the top of the file.

var module = {
    exports: {}
};
var exports = module.exports;

So now we can simply use exports and append all kinds of properties and functions to it. For example, let’s create a user module and use it in our application. You can find the source code for this on GitHub.

exports.firstName = null;
exports.lastName = null;
exports.birthDate = null;

exports.getFullName = function() {
    return exports.firstName + ' ' + exports.lastName;
};

exports.getAge = function() {
    // I admit I had to look this one up...
    // http://www.scriptol.com/javascript/dates-difference.php
    return new Number((new Date().getTime() - exports.birthDate.getTime()) / 31536000000).toFixed(0);
};

And now we can use it like this.

var http = require('http');
var user = require('user_export');

user.firstName = 'Sander';
user.lastName = 'Rossel';
user.birthDate = new Date(1987, 11, 8);

var server = http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end(user.getFullName() + ' is ' + user.getAge() + ' years old.');
});

server.listen(1337, '127.0.0.1');

So that’s awesome! But let’s add another user. We might go about it as follows.

var http = require('http');
var user1 = require('user_export');
var user2 = require('user_export');

user1.firstName = 'Sander';
user1.lastName = 'Rossel';
user1.birthDate = new Date(1987, 11, 8);

// Creator of JavaScript.
user2.firstName = 'Brendan';
user2.lastName = 'Eich';
// Don't know his exact birthdate...
user2.birthDate = new Date(1961, 1, 1);

var server = http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end(user1.getFullName() + ' is ' + user1.getAge() + ' years old.' +
    '\n' + user2.getFullName() + ' is ' + user2.getAge() + ' years old.');
});

server.listen(1337, '127.0.0.1');

Now if you run this you’ll notice that this is completely wrong! We can’t have more than one instance of user, so now both users are actually Brendan Eich!

So our module is not very re-usable… But remember that I said that require will just return the exports object? How about if we just set the exports object to a constructor for our user object? The module would now look like this.

module.exports = function User(firstName, lastName, birthDate) {
    var self = this;
    self.firstName = firstName;
    self.lastName = lastName;
    self.birthDate = birthDate;
 
    self.getFullName = function() {
        return self.firstName + ' ' + self.lastName;
    };

    self.getAge = function() {
    // I admit I had to look this one up...
    // http://www.scriptol.com/javascript/dates-difference.php
        return new Number((new Date().getTime() - self.birthDate.getTime()) / 31536000000).toFixed(0);
    };
};

Notice that I’m using module.exports! Setting the exports shorthand wouldn’t work here as it is module.exports that is loaded by require! exports is just a shorthand. It references the same object as module.exports, but it is not module.exports. This is a very important difference. If you’re not sure what to use just use module.exports and you’re safe.

So we’re now loading a function with require. How does that look?

var http = require('http');
var user = require('user');

var user1 = new user('Sander', 'Rossel', new Date(1987, 11, 8));

// Creator of JavaScript.
// Don't know his exact birthdate...
var user2 = new user('Brendan', 'Eich', new Date(1961, 1, 1));

var server = http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end(user1.getFullName() + ' is ' + user1.getAge() + ' years old.' +
    '\n' + user2.getFullName() + ' is ' + user2.getAge() + ' years old.');
});

server.listen(1337, '127.0.0.1');

The code became a little cleaner, but more importantly, I can now have two instances of the user object!

And of course you can require in modules too. Try putting the following in a module.

var http = require('http');

exports.startServer = function() {
    var server = http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Server was started from module!');
 });

    server.listen(1337, '127.0.0.1');
}

And to try that out.

require('start_server').startServer();

Events

Another important aspect of Node.js is Events. If you’ve worked with .NET, and especially WinForms, you should be familiar with events already. In JavaScript events are usually implemented as callbacks, a function that is called when a certain action completes. Node.js has a special module that handles events.

Let’s implement a basic event.

var http = require('http');
var EventEmitter = require('events').EventEmitter;
var emitter = new EventEmitter();

emitter.on('request', function(url) {
    console.log('requested ' + url);
});

var server = http.createServer(function (req, res) {
    emitter.emit('request', req.url);
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('url logged to console.');
});

server.listen(1337, '127.0.0.1');

So as you can see we start by requiring the events module. We then create a new instance of the EventEmitter class. To create an event simply use the on method and pass it the name of the event and a function that should be executed when the event triggers. To actually trigger the event call the emit method and pass it the name of the event and the event data.

It is totally acceptable to add multiple handlers to the same event.

var http = require('http');
var EventEmitter = require('events').EventEmitter;
var emitter = new EventEmitter();

emitter.on('request', function(url) {
    console.log('requested ' + url);
});

emitter.on('request', function(url) {
    console.log('second listener, received request ' + url);
});

var server = http.createServer(function (req, res) {
    emitter.emit('request', req.url);
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('url logged to console.');
});

server.listen(1337, '127.0.0.1');

It’s also possible to handle an event only once using the once method.

emitter.once('request', function(url) {
    console.log('one time listener, received request ' + url);
});

And you can remove listeners as well using the removeListener function. To remove a listener you need to pass in the listening function, so we cannot start listening using an anonymous function like I did up til now. So in the following example I declare a function, add it to my emitter and then remove it after three server requests.

var http = require('http');
var EventEmitter = require('events').EventEmitter;
var emitter = new EventEmitter();

var removableEvent = function(url, counter) {
    console.log('this event will be removed in ' + counter + '...');
};

emitter.on('request', removableEvent);

var counter = 3;
var server = http.createServer(function (req, res) {
    emitter.emit('request', req.url, counter);
    counter--;
    if (counter === 0) {
        emitter.removeListener('request', removableEvent);
    };
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('url logged to console.');
});

server.listen(1337, '127.0.0.1');

And of course any event emitter can have as many events as you want and trigger them in different places.

var http = require('http');
var EventEmitter = require('events').EventEmitter;
var emitter = new EventEmitter();

emitter.on('request', function(url) {
    console.log('requested ' + url);
});

emitter.on('message', function(message) {
    console.log('Received message: ' + message);
});

var server = http.createServer(function (req, res) {
    emitter.emit('request', req.url, counter);
    emitter.emit('message', 'Received request for ' + req.url);
 
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('url logged to console.');
});

server.listen(1337, '127.0.0.1');
emitter.emit('message', 'Server started and listening on 127.0.0.1:1337');

So as you see working with events isn’t very difficult, you just have to know how it works.

This was my third article in the MEAN series and the second one on Node.js. There’s a lot to say about Node.js, in fact I’m not quite done yet! We’ll look at more Node.js goodness in upcoming articles. I do want to move on to the other letters of MEAN as well though. So for my next article I’m going for either M (MongoDB) or E (Express.js). Both require more Node.js. So if you have any preference let me know! M or E, most votes wins. For no votes or a tie I’m simply going to pick one myself.

And again I’m going to recommend some books, just in case you missed them in¬†my previous articles. Be sure to get¬†Node.js Succinctly from Syncfusion, it’s free and the subscription is totally worth it since they have lots more free ebooks!
For a bit more in depth Node.js knowledge I can recommend Mannings Node.js In Practice, Node.js In Action or Getting MEAN With Mongo, Express, Angular, And Node. They’re not free, but Manning provides value for your buck!

That’s it for this week. I hope to see you back next week for either MongoDB or Express.js (be sure to let me know what you want!).

Stay tuned!

MEAN web development #2: Node.js in the back

A series on MEAN and the first actual article in which we’ll get some web pages served starts with the N, the very last letter of MEAN! Yes, it’s true, we’re starting in the back, literally and figuratively speaking. Node.js will be your server side software and you’ll use it to handle incoming HTTP requests. Once we’ve got this going we’ll be able to get to the other letters of MEAN (MongoDB, Express and AngularJS in case you forgot). And in fact we’ll already be looking at some of that E, for Express, in this post!

For a change I won’t mention you should follow me on Twitter because that’s where I tweet on anything software, MEAN and Node.js related and I won’t mention my Twitter handle is @sanderrossel either.
So now that I haven’t mentioned that I am going to mention my GitHub account because that’s where you’ll find the source code for this blog post. You can find the repository for this post in the¬†SanderRossel/mean2-blog¬†repository.

By the way, if you’re just dropping in and you haven’t read the first post in this series yet you really should.

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

Getting started

Maybe the title of this post seems familiar? I’ve written on a back-end technology before, Web development #4: PHP in the back. In that blog post I explain how to write PHP and how to get it working on your own machine by installing some web server software, XAMPP. Here’s the cool thing about Node.js. It is a web server already, so you don’t need to install anything besides Node.js (which we did in the first part of this series). You can just write JavaScript and run your server!

So let’s look at the “Hello world” example from the first article again.

var http = require('http');
var server = http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello, Node.js!');
});
server.listen(1337, '127.0.0.1');
console.log('Server running at http://127.0.0.1:1337/');

I’ve written it a bit different from my first post, so we can see what’s going on just a little bit better. There are a few things going on there. First of all is the ‘require‘ bit. With require we can load a module which we can use to implement certain functionality. So what’s a module? Node.js has a pretty cool module system, where a module can be compared to classes like we have in C# or Java. We’ll look at modules in more detail in a next post. So anyway, with the first line of code we’re telling Node.js that we need the http module and we store it in the http variable.

So now that we have this http module, or class-like thing, we can invoke functions on it. And the first (and only) function we’re going to call is createServer. So createServer takes an (optional) callback function as parameter. The callback function¬†takes a request and a response as input parameters which we can use to see what the user requested and to return anything back to the client.
As you can see we’re writing to the header of the response, using writeHead, to tell it that everything was handled correctly (HTTP code 200 is OK) and that we’re sending back some plain text. By calling response.end we’re telling Node.js we’re done and that the result is ready. Response.end must be called on each request (or our client will be waiting on a response forever) and it must be called as the final operation on our response object, since it signals that the response is complete (all headers and content have been written to the response). In this case we’re passing¬†our response text directly to the end function, but alternatively we could use the write function and simply call end without parameters. That would look as follows.

res.writeHead(200, {'Content-Type': 'text/plain'});
res.write('Hello, Node.js!');
res.end();

Or, if you want to build up some response text, you can do something as follows (using write n times).

res.writeHead(200, {'Content-Type': 'text/plain'});
res.write('Hello,');
res.write(' Node.js!');
res.end(' [This text is optional]');

And, of course, we’ll typically return HTML rather than plain text. Notice I’ve changed the header too.

res.writeHead(200, {'Content-Type': 'text/html'});
res.end('<h1>Hello, Node.js!</h1><p>This is a paragraph...</p>');

So now that we’ve called the createServer function and we’ve specified what to return we have a Server object. This Server object has functionality to listen for incoming HTTP requests and handle them accordingly. To start listening simply call the listen function and pass it a port and an IP address. I’m still using 1337 and localhost from the Node.js website example.

Last, and actually also least, is the console.log, which just logs some debug info to your command window when starting your Node.js app.

You can run each example by opening up a command prompt and typing in (exluding double quotes (“”)) “node pathToMyFile\MyFile.js”. If your file path contains any spaces be sure to wrap it in double quotes.

Debugging

Did you try out all those examples? Did you have to restart the command prompt and type in “node pathToMyFile\MyFile.js” a couple of times? Tiresome, isn’t it? Luckily there are tools that automatically restart your Node.js app when changing a file. You really should install one and save yourself time and trouble! I’m going to use nodemon. You can install it using npm. Open up a command window and type “npm install nodemon -g”. The -g tells npm to install nodemon globally. That means nodemon isn’t some library that this one project uses, it’s a global library from which all your projects can benefit! Whoohoo, never again restart your Node.js app manually because you’ve made a minor file change! To make sure nodemon installed correctly open up a command prompt and type in “nodemon -v” and you should get the currently installed version of nodemon.
Now instead of starting your Node.js app using “node pathToMyFile\MyFile.js” use “nodemon pathToMyFile\MyFile.js” (simply replace node with nodemon). Now go ahead and edit your file. Watch the command prompt and see how your app is automatically restarted. Browse to your website (localhost:1337) and see that the Node.js app has indeed restarted.

For some more tips¬†on debugging web apps in general (no matter if you’re using Node.js, C# ASP.NET, Java or what have you) you should read a previous blog post I wrote, which has a little section on debugging web pages from your browser, Web development #8: Where to go from here.

Doing a little more

So here’s a nice one for you.

res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Requested: ' + req.method + ' - ' + req.url);

Try putting that in the createServer callback. Now browse to localhost:1337/SomePage or localhost:1337/AnotherPage?someParam=someValue. You should see whatever you put after localhost:1337 echoed in your browser window.

So let’s say we have some HTML pages that we want to show based on the requested page. This is now pretty easy. Here’s a first, and rather naive, implementation. In case you got my source from GitHub, the final implementation can be found in the file nope.js (that kind of gives away the ending, doesn’t it?).

var http = require('http');
var fs = require('fs');

var server = http.createServer(function (req, res) {
    switch (req.url) {
        case '/about.html':
            res.writeHead(200, {'Content-Type': 'text/html'});
            var buffer = fs.readFileSync(__dirname + '\\about.html');
            res.end(buffer.toString());
            break;
        case '/index.html':
        case '/':
            res.writeHead(200, {'Content-Type': 'text/html'});
            var buffer = fs.readFileSync(__dirname + '\\index.html');
            res.end(buffer.toString());
            break;
        default:
            res.writeHead(404, {'Content-Type': 'text/html'});
            res.end('<h1>404 - Page not found!</h1><p>What were you even trying to do...?</p>');
            break;
    }
});
server.listen(1337, '127.0.0.1');
console.log('Server running at http://127.0.0.1:1337/');

So there’s some new stuff in there. First we¬†require(‘fs’), which gives us some control over the file system (fs is short for File System). After that we do a switch statement on the request url. We support no url (just localhost/1337, we’ll get url “/”), /index.html and about.html. Everything else will get a 404, page not found. Note that no url and index.html both give you the index.html page. So make sure you have an index.html and an about.html page in the same folder as your Node.js app. If you got this from my GitHub account you’ll be fine, otherwise you’ll need to create those files and put some HTML in them.
So if you browse to localhost:1337/index.html or about.html we’ll first set the header to 200 and text/html. After that we’ll use the fs object to read either the index.html or the about.html file.
Notice that I’m using readFileSync. Remember that I explained, in my first post in the series, that Node.js runs a single thread to handle all incoming requests? Because any synchronous action (meaning it just runs on the same thread) is blocking that one thread everything in Node.js is asynchronous by default. So any non-asynchronous (synchronous) method is suffixed with ‘Sync’. If, like me, you’re coming from C# that’s just the other way around from what you’re used to!
So anyway, we read the file and we now get some buffer object. To get the actual contents as a string simply call the toString function on the buffer.
We also see the __dirName variable, which is a global Node.js variable which contains the directory in which your Node.js JavaScript file resides.

There is an overload for the readFileSync that will return the string value instead of the Buffer object.

var content = fs.readFileSync(__dirname + '\\index.html', 'utf8');
res.end(content);

So there are a few problems with this code. First of all we are reading files synchronously. Suppose this takes 50 milliseconds. No big deal you’d say, but suppose you have 100 requests per second, that’s 5000 milliseconds, or 5 seconds, for the 100th visitor! Imagine that every 100th visitor had to wait 5 seconds, at least, for your page to load. That’s rather disastrous for a web page! So we really want to read that file asynchronous. Luckily that’s pretty easy. We can use the readFile function which takes a callback function as last parameter. The callback function gets an error object and the returned data as input parameters. So how would that look?

fs.readFile(__dirname + '\\index.html', 'utf8',
    function (err, data) {
        if (err) {
            // Handle exception...
        } else {
            res.writeHead(200, {'Content-Type': 'text/html'});
            res.end(data);
        }
});

Second, we’d best put the file handling in a seperate function. We now have this ‘huge’ piece of duplicated code! So let’s tidy it up a bit.

var http = require('http');
var fs = require('fs');

var readHtml = function (fileName, res) {
    fs.readFile(__dirname + '\\' + fileName, 'utf8',
        function (err, data) {
            if (err) {
                // Handle exception...
            } else {
                res.writeHead(200, {'Content-Type': 'text/html'});
                res.end(data);
            }
    });
};

var server = http.createServer(function (req, res) {
    switch (req.url) {
        case '/about.html':
            readHtml('about.html', res);
            break;
        case '/index.html':
        case '/':
            readHtml('index.html', res);
            break;
        default:
            res.writeHead(404, {'Content-Type': 'text/html'});
            res.end('<h1>404 - Page not found!</h1><p>What were you even trying to do...?</p>');
            break;
    }
});
server.listen(1337, '127.0.0.1');
console.log('Server running at http://127.0.0.1:1337/');

So, all fixed, right? Well, actually, this looks more like Nope.js! Well alright, I suppose it’s not that bad, but once your app starts to get bigger this approach might get a little messy. Let’s add some Express and see how it can help make things easier.

Just a little remark on the 404 HTML. Of course it would be¬†better to create another HTML file for the 404 page, but I just wanted to show you that you can use multiple methods of returning HTML even if you’ve already used another method.

Adding some Express

In the first part of this series we’ve installed Express in our project, so I’m assuming you’ve got it set up. As said Express just makes working with Node.js a lot easier. It handles routing, rendering of HTML, sessions, template engines and all that stuff. So let’s rewrite the above code so it uses Express.

var express = require('express');
var app = express();

var options = {
    root: __dirname
}

app.get(['/', '/index.html'], function (req, res) {
    res.sendFile('index.html', options);
});
app.get('/about.html', function (req, res) {
    res.sendFile('about.html', options);
});
app.get('*', function (req, res) {
    res.send('<h1>404 - Page not found!</h1><p>What were you even trying to do...?</p>'); 
});

var server = app.listen(1337, '127.0.0.1');

First we’re requiring Express. This actually doesn’t return an object, but a function, also called the express function, and as you can see on the second line we just run the function and store the result in our app variable. This app variable now denotes our Express application. After that we use the app.get function multiple times to handle our routing. I think it’s pretty straightforward. If “/” or “/index” are requested we return the index.html file, if “/about” is requested we return the about.html file and if anything else is requested we send back the 404 HTML.
It’s worth mentioning that the send and sendFile functions set the header of the response object. sendFile sets the header based on the file extension (in these cases .html) and you can override it in the options object. We only use the options object to set the root of the files though, in our case that’s the same folder as our app resides in, but for bigger projects it would be wise to create a /views folder or something like that.
Finally we call app.listen and pass in our port and IP address. Notice I’ve used the same port and IP as the nope.js¬†example, so you can’t run them both simultaneously.

Here’s another thing Express handles pretty well. Parameters and queries. Using the request object we can ask for any parameter or query that the user sent our way. Here a little example.

app.get('/echo.html', function (req, res) {
    res.send('<h1>Echo</h1><p>This is an echo... ' + req.query.say + '</p>');
});

Using the query object we can get the value of any query parameter. In this case we expect a parameter called “say” and its value will be echoed to your browser. So just browse to localhost:1337/echo.html?say=someValue.
Pretty neat, right?

There are some other best practices, like putting your routing in a separate file and exception handling, that we haven’t discussed yet. No problem, since we’ve only scratched the surface anyway. Don’t worry, we’ll go in a little deeper yet in my next post!

And as always I’d like to give you some reading recommendations. Syncfusion has an awesome free ebook on Node.js, Node.js Succinctly. Just sign up and get them free Succinctly books! They have lots more, like JavaScript Succinctly and HTTP Succinctly, which might come in handy when working with Node.js.
And it also just so happens that Manning Publications has quite a few books on the MEAN stack as well! They’re not free, but when you really want to do some Node.js heavy lifting I can really recommend getting one of them. So they’re Node.js in Action, Node.js in Practice and Express.js in Action.
And, of course, you could also just keep following my blog, which is free and a lot less to read.

Stay tuned!

MEAN web development #1: MEAN, the what and why

Yes, a new blog post and a new series! I apologize for not writing a post last week, I was a bit busy. I’ll try to make it up to you by starting an awesome series on MEAN web development.
I’ve been tweeting on MEAN and related technologies on Twitter, so be sure to follow me @sanderrossel as well.

But what is MEAN and why would you want to know and use it? That’s what we’ll look at in this first episode. We’ll also set up our environment. In the following posts we’ll look at each technology involved with MEAN in more detail.

  1. MEAN web development #1: MEAN, the what and why
  2. MEAN web development #2: Node.js in the back
  3. MEAN web development #3: More Node.js
  4. MEAN web development #4: All aboard the Node.js Express!
  5. MEAN web development #5: Jade and Express
  6. MEAN web development #6: AngularJS in the front
  7. MEAN web development #7: MongoDB and Mongoose
  8. MEAN web development #8: Sockets will rock your socks!
  9. MEAN web development #9: Some last remarks

 The what

So what is MEAN? I could call you dumb for not knowing, that would be mean (and unjustified, because you’ll know within seconds), but that’s not quite the mean¬†I’m talking about! MEAN is actually an acronym (because we love acronyms in IT) and it stands for MongoDB, Express, AngularJS and Node.js. Chances are you’ve heard of those and if you read a previous blog post of mine, Web development #8: Where to go from here, you even know a little bit about what they are (although you could’ve got that from other sources too, of course).
In short, MongoDB is a NoSQL Document Model database, Node.js is a¬†platform that allows you to run JavaScript on/as your web server, Express is a library that simplifies working with Node.js and AngularJS is a front end framework that let’s you create Single Page Applications (SPAs).

Don’t worry, we’ll look at all of them in much more detail later. In fact, I’ve already written on MongoDB in an earlier blog post, A first look at NoSQL and MongoDB in particular. Actually I’m going to ask you to read that post in a little bit.

So here’s the deal, MongoDB is a database that doesn’t use SQL, but JavaScript, as a query language, Node.js is a platform that let’s you use JavaScript on your back end, AngularJS is a JavaScript library for your front end and Express is just a library for Node.js. So that’s JavaScript across your entire stack! That’s pretty awesome, especially when you’re a fan of JavaScript.

You’re probably going to use more than just MEAN. MEAN is just a starting point, but, of course, you’re free to add (or remove) whatever you like. Perhaps a little jQuery UI, a¬†HTML generator like Jade, ¬†or sockets.io, a library for working with sockets in Node.js.

The why

So why would you use MEAN over other technologies? Here’s the thing, I’m not religious about any technology and you can probably do anything you can do with MEAN with other technologies as well. SQL Server and C# would do nicely, especially when throwing in SignalR, but then of course you’d have SQL in your database, C# on your back end and JavaScript in your browser. So just being able to stick with one language (unfortunately that language is JavaScript) could be considered a pro.

Let’s look at why you’d want to use any of the MEAN letters seperately.
MongoDB is a very flexible database that looks a little like the relational¬†databases you already know. MongoDB is schemaless though, so adding any field becomes a breeze (no production downtime!). That’s especially neat when you have huge tables with lots of data. I know adding a field to any SQL database can be¬†quite a challenge on big tables, because your entire table has¬†to be updated. On top of that MongoDB scales well, much better than most SQL databases. Actually let’s stop on why you’d want to use MongoDB, just read my NoSQL and MongoDB article, A first look at NoSQL and MongoDB in particular.

Node.js is really an alternative to popular web servers such as Apache or IIS (Internet Information Services). So how is Node.js different than those two (and others)? Well, Apache and IIS both listen to incoming HTTP requests using threads. So that means a number of different little ‘processes’ (the threads) are listening for incoming requests and handle them. That means that if all threads are busy no new requests can be handled at that time and your server response becomes slower.
Node.js, in contrast, uses only a single thread to listen for incoming HTTP requests. What it does is listen for an incoming request, put it on a stack, and handle it on a different thread. This process is so fast (if you do it right) that Node.js should be able to handle more concurrent connections than Apache or IIS. Of course if you mess up in Node.js you’ll be blocking the server for everyone else too.
And if you’re going to use Node.js you’re probably going to use Express as well as it really makes Node.js development easier (but you’re entirely free to do a little ‘MAN’ development, of course ūüôā ).

And why would you want to use AngularJS? AngularJS is a¬†framework for creating Single Page Applications. On ‘traditional’ web pages your page needs to refresh entirely for each server request. So imagine you’re at some web shop and you’re reading product reviews. There’s ten reviews per page and you’ve just read the tenth. When you click on ‘next page’ the entire page gets refreshed. So the server sends the entire HTML, the product images (if they’re not cached by your browser), the product description, other recommended products, etc. to your browser. That’s a whole lot of information you already had! In a SPA you’d only send the ten new product reviews and replace the old ones with the new ones in your browser (for example using jQuery, or AngularJS).
So a SPA, when done well, is a lot faster and better usable than a traditional application. Of course you may use jQuery for AJAX requests and DOM manipulation, but AngularJS is a framework that was kind of built to handle these exact cases, whereas jQuery is more general. So AngularJS could be a good choice when building SPAs. Of course you can replace AngularJS with another framework if you like, perhaps Ember.js or Backbone.js, you could be doing MEEN or MEBN development (I’m really just making that up, but why not, right?).

So put that together and MEAN is just an all-JavaScript stack that’s fast, responsive and flexible. Did I mention it’s all open source, so free to use? That’s pretty awesome!

Setting up your environment

MongoDB

Let’s get to work, shall we? Let’s start with setting up MongoDB. As I mentioned I’ve already written on MongoDB in a previous post, A first look at NoSQL and MongoDB in particular. As luck has it I’ve also described how to set up MongoDB, so I suggest you read that post and especially the “Getting started with MongoDB” bit (you can skip the C# part). Little has changed since I wrote that post some months ago, but I’ll briefly discuss the differences. You can download MongoDB from the downloads page. The default install path has changed to “C:\Program Files\MongoDB\Server\3.0\bin”. You can run MongoDB through the command line or by running mongod.exe directly.
You should also install MongoVUE, as described in the blog post. I’ll be using it for this series anyway. When first starting MongoVUE you need to specify a connection. Give it any name you like, set ‘localhost’ as server and you’re good to go. Other than that I think MongoVUE is pretty self explanatory, especially when you’ve used SQL Server.

Node.js

So let’s set up Node.js next. Head over to nodejs.org and click the big green install button. It should give you the installer for your system (I’m assuming you’re on a Windows machine). You can, of course, also select an installer manually by heading over to the downloads page. Then just run the installer and make sure you also install the npm¬†package manager. Actually, just install everything. Once it’s installed you can run any Node.js application (which is really just a JavaScript, or .js, file) from the command prompt. And while we’re on the subject I want to coin a new term CPDD, Command Prompt Driven Development (ok, that was a joke). Why are we still using command prompts in 2015!? So I’m not a fan of command prompts because it’s a lot of typing and I always forget what to type. If you’re like me, no worries, I’ve got you covered!

So while we’re at it let’s create a very simple hello world! We’ll see Node.js in action and we’ll be able to fire it up using the command prompt. So first we’ll create a folder for our ‘project’. I’ve put it in C:\dev\hellonode\ and there I’ve created a file called hellonode.js. Now put the following code in that file.

var http = require('http');
http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello, Node.js!');
}).listen(1337, '127.0.0.1');
console.log('Server running at http://127.0.0.1:1337/');

As you can see¬†it’s just JavaScript. The example was taken from the Node.js homepage. So we first create an instance of the http module by invoking¬†the require function and pass in the string (id) ‘http’. When we have our http object we invoke the createServer function and pass in a function as only parameter. The function has a request (the HTTP request) and a response¬†as parameters. So whenever the server receives an HTTP request this function is called and we can inspect the method (GET, POST etc.) and any parameters and basically anything that was sent with the request. We’re not really interested¬†in any of that here though since we’re just going to send the same result every time a request is made. We write HTTP code 200 (OK) and the content type text to the result header and we end the request by invoking the end function and passing it the text ‘Hello, Node.js!’.
The function createServer returns a Server object. We invoke listen on this Server object, pass in a port and IP address (localhost in the example) and at that point our server goes up and running and listens for requests.

Don’t worry if you didn’t get that. We’ll look at Node.js in much more detail in a later post. So now to get this running. Open up a command prompt and type in the following (excluding double quotes “”): “node C:\dev\hellonode\hellonode.js” and you should see that your server is running. Now browse to localhost:1337 and you should see “Hello, Node.js!” in your browser window.
Congrats, you just created your first Node.js app!

Express and npm

So next we need to install Express. We’ll do this using npm. npm is a JavaScript package manager¬†and it’s the default package manager for Node.js. There¬†are¬†alternatives, like Bower, but let’s just stick to npm. So open up another command prompt (argh!). First we want to make sure npm is on the latest version. We can issue an update command with the following command “npm install npm -g”. After that move to the folder that holds your project using command “cd C:\dev\hellonode” and then use the command “npm install express” to actually install Express to your project. To uninstall express you can use the command “npm uninstall express”.
Alternatively you can create a small file called package.json and put the following JSON in it.

{
  "name": "hellonode",
  "version": "1.0.0"
}

Now when installing or uninstalling a package add –save at the end of your command, like so “npm install express –save” and “npm uninstall express –save” and npm will keep track of dependencies in this file. For example when installing Express your packages.json file will look as follows.

{
  "name": "hellonode",
  "version": "1.0.0",
  "dependencies": {
    "express": "^4.12.3"
  }
}

So to make sure it really works you can create a JavaScript file called helloexpress.js¬†and try out the Hello world example from the Express “Hello World” example page. Try it out by running the following command from a command prompt: “node C:\devhellonode\helloexpress.js” and browsing to localhost:3000.

So that’s it! We’ve got a little bird’s eye view on MEAN and we’ve got both MongoDB and Node.js up and running and we’ve installed Express using npm. I’m not discussing AngularJS here because we’ve seen how to add front end libraries to our pages in previous blog posts, for example Web development #6: Getting interactive with JavaScript. We’ll get to setting up AngularJS anyway when I post about it.

In next posts we’ll look at MongoDB, Node.js, Express and AngularJS in much more detail and we’ll see how they work together.
In the meantime, if you’re interested in knowing more about any of those I can really recommend the free ebooks by Syncfusion¬†(yeah, here we go again). They¬†have books on all the MEAN parts, MongoDB Succinctly, Node.js Succinctly and AngularJS succinctly. ¬†You have to sign up, but it’s free and really worth it.
If you really want to get into it I can recommend some books by Manning Publications. They have books on all the seperate technologies, but they also have an upcoming book on the entire MEAN stack, Getting MEAN with Mongo, Express, Angular, and Node.
I’m looking forward to reading your comments and¬†I hope to see you back with the next installment.

Stay tuned!