Category Archives: javascript

Getting my Mongo on

This is the sixth post in a small series on Node.js. In this post, I will take a look at how to use my MongoDB from a Node app.

First, let’s install a driver for MongoDB: node-mongodb-native:

NPM really make it easy to get going!

Now, in order to connect to MongoDB, do this:

This should be done only once when the application starts up.

Then, to access a collection, do this:

Inside the function above, coll gives you access to do all the usual stuff to a MongoDB collection. To name a few, there’s insert, find, findOne, ensureIndex, count, etc.

As the node-mongodb-native documentation is pretty sparse, I’ve found it useful to open up a Node.js shell and connect with the driver, allowing me to inspect the various objects’ properties and methods, e.g. by inspecting db.__proto__ like so:

and coll.__proto__ like so:

Of course this way of barfing functions all over the place is not pretty, but it makes it possible to get a glimpse of what kinds of operations that can be performed on the various objects.

What is that module thing again?

This is the fourth post in a small series on Node.js. In this post, I will take a look at how the Node.js module mechanism works.

In my previous posts on Node.js, I nonchalantly went ahead and require(...)d something called http – but what was that? And what happened when I did that?

Well, require is one of the few globals when running a Node program, and it is used to import a module. The parameter is a string, which Node uses to look for a file to load.

The simplest usage refers directly to a file relative to the path of the currently running program. E.g., if I have a module residing in a file called importantBizLogic.js in the lib folder beneath my program’s directory, I can include its exports (which I’ll get back to in a moment :)) like so:

If I omit the ./, Node will go look for importantBizLogic in each directory in the require.paths array, which is a list of default paths to search for modules.

Let’s see what it contains… Go to a terminal and enter the Node shell:

Great – so that’ s where my global modules reside. Now, what was that export thing again?

Well, that’s related to how importantBizLogic.js is structured… in order to control how the import works, a module must explicitly export stuff – and that can be done like so:

- allowing this module to be imported and used like so:


Apparently – and I am almost embarrassed that I did not know that – there is a thing called CommonJS, which is an initiative that strives to create a JavaScript standards library – and the require stuff I’ve described here is actually just Node implementating the CommonJS Modules specification. Pretty sweet, actually!

Up and running with Express

This is the third post in a small series on Node.js. In this post, I will take a look at how to get up and running with Express.

Let’s get Express installed – first, let’s install NPM – a package manager for Node:

That was easy. Now, Express can installed like this:

Too easy!

Now, let’s create a simple app like we did the last time:

Punch in the following few lines:

and run the app from the terminal like so:

and navigate to http://localhost:3000 – on my machine it looked like this:
Hello Express

That was easy. See how the API pretty much resembles Node’s builtin HTTP server, except it adds routes into the mix!

Now, in order to build a web site we need some kind of view engine to help generate some HTML for us. I have used Haml a couple of years ago, and I really liked it… and luckily, some nice people have made Haml available to Node apps, so let’s try installing that:

Now we configure Express by punching in the following stuff in the app:

As you can see, I tell Express to use Haml as the default view engine. Moreover, I configure Express to serve static content from the /public folder in my app dir, and then I install the bodyDecoder middleware which will parse incoming posts and make posted values available in req.body.

Now, let’s alter our action to render a view:

and now create two files, layout.haml and index.haml in the /views folder. Mine look like this – /views/layout.haml:

and /views/index.haml:

Now, let’s go to the terminal and node app.js and navigate to http://localhost:3000 – on my computer it looks like this:
Hello Express + Haml

As you can see, view models can be handed to the view via the locals object.

This was some basic web app stuff – only thing missing is some way to persist data, so next time I will take a look at how to get my Mongo on…

Getting started with Node.js

This is the second post in a small series on Node.js. In this post, I will take a look at how to get started and run the ubiquitous “Hello world” sample.

First, create a directory somewhere and Git clone Node… I did it like this:

Then, build and install Node like this:

If you get permission errors during the last step, you might need to do a

to grant yourself ownership of everything beneath /usr/local. Note however, that this should probably only be done if the machine is your own personal machine.

Now, try typing node -v in the terminal… I got this:

Now, let’s finish this post by creating a Node app like so (using TextMate or whatever you prefer):

Punch in the following few lines:

and go the terminal again and type

which yields

Now, when I navigate to http://localhost:8124 I get this:

Node.js HTTP Hello World

Nifty, huh?

In the next post, I will see if I can get up and running with Express – a simple but powerful Sinatra-like web framework for Node.

I want to learn Node.js


More than three years ago, I watched a couple of videos with Douglas Crockford that changed my view on JavaScript completely!

I must admit that I too used to consider JavaScript a toy language, somehow inferior to “real programming languages” like Java and C#.

This view was of course induced by the sheer amount of JavaScript crap code available to copy/paste from the web, almost always operating on an equally crappy non-standards compliant DOM implementation in some crappy browser – but after watching those videos I actually began to understand that JavaScript was a pretty cool and powerful language.

Some time after, Crockford released JavaScript: The Good Parts which I immediately read, and at that time I remember saying to one of my colleagues: “I think it would be cool to build large systems in JavaScript”.

At that time, stuff like Rhino was around, but I had never heard of anyone actually using it, and executing JavaScript on the JVM by compiling JavaScript into Java into bytecode didn’t sound sexy at all to me.


Recently, however, I have somehow come across Node.js at different occasions, and I have really been meaning to check it out. If you don’t know what Node is about, I can quote the homepage: Node is “Evented I/O for V8 JavaScript.”

That’s right! Let’s break that down:

  • Evented: There’s only one thread executing in a Node process, high throughput is achieved by doing asyncronous I/O, queueing callbacks to be executed upon completion.
  • I/O: Not usually what JavaScript is used for, but this covers the fact that Node has APIs that treat the file system and TCP and HTTP as first class citizens.
  • V8: The JavaScript is executed by the V8 JavaScript Engine that Google in Aarhus built for Chrome.

As an example, there’s the ubiquitous code sample that you’ll see everywhere – opening a HTTP server in Node:

As you can see, Node has a nice and thin API for working with HTTP, and as I envy Rubyists of having Rack and Sinatra, and as I am interested in how web frameworks work in general, this code sample has continued to spark my interest.

Therefore, in order to push myself through learning more about it, I have decided to see if I can write a couple of blog posts on Node.js. I will try to cover the necessary topics to develop a simple web app, and I expect to come across more or less of the following:

  • Acquiring Node.js and running a “Hello world” script. Can’t do anything without having done this.
  • Basic Node stuff, like how to structure code into files/modules/whatever and whatnot.
  • Bringing in external, possibly native libraries.
  • Building a web app, possibly with Express – a simple web framework for Node.
  • Persisting some data, probably using node-mongodb – a MongoDB driver for Node.
  • Unit testing my app – probably with the built-in assert API.
  • Hosting my app – probably with Nginx as a router and load balancer.

Wow! – that was a lot of words and almost no code… I promise that my next posts on Node will have more code in them.