I Am Simme

Random musings by a programmer and film photography geek.

Taking advantage of Node's require algorithm with Browserify

Posted in JavaScript.

This morning I read a post written by Paolo Fragomeni. In it he describes how he builds stuff without using a framework. The part that was really eye opening to me though, was the fact that you can have a node_modules directory in other places than in the root of your project.

Thinking about it it seems kind of obvious. However, it is an easy thing to overlook. Paolo didn't dive too deeply into the nitty gritty details, so I'll lay it out in this post.

Here's the gist of it. Say you have a folder structure that looks like this:

my-app/  
  assets/
    js/
      node_modules/
        .. your custom front-end modules
      main.js
  node_modues/
    .. lots of modules

Say main.js looks something like this:

var Application = require('application');  
var app = new Application();  
app.boostrap();  

And then you use Browserify to build this with something like:

browserify assets/js/main.js > build/app.js  

Now.. where does application live? How does Browserify find it? The long answer is described in the Node.js documentation for loading modules. The short answer is: first we look in the node_modules folder inside of the assets folder. If the module we're looking for cannot be found there Node (or Browserify in our case) starts walking up the directory tree looking for another node_modules folder.

So our theoretical application module might live in my-app/assets/js/node_modules/application/. In this folder there'd be an index.js file that looks something like this perhaps:

module.exports = Application;

function Application() {  
  // Some setup logic and stuff.
}

Application.prototype.bootstrap = function () {  
  // Magic
};

The thing I don't like about this approach is that it creates tons of index.js files, which might make it hard to tell file from file in your editor or whatever. So what I like to do is to actually have a package.json for each module with only two properties. Like so:

{
  "name": "application",
  "main": "application.js"
}

This way the module file can be application.js. You end up with a lot of package files instead, but I can live with that.

Grouping Modules

One pattern that you might be accustomed to is to group models in one directory, views in one directory, helpers in one etc. You can still do that! Simply by putting your modules inside directories.

node_modules/  
  models/
    user-model/
    article-model/
  views/
    user-view/

Now, to rewuire the user-model module, for example, you'd do: require('models/user-model'); Notice the lack of ./ or even worse ../ in front of the model path. Regardless of from where you are calling require this will still work. Since Browserify will look inside your node_modules folder by default!

.gitignore

If you're like me then you like to ignore the node_modules folder by default. But since in this case the folder would actually contain code that you might not publish as individual modules you probably also want to commit them to you project repo. Easy! Just put !assets/js/node_modules in your .gitignore and commit away!

Conclusion

Not having to worry about relative path's inside your require statements is a huge boost to code clarity. I really like this approach and will continue experimenting with it!

Also, remember that this applies to Node.js code as well, it's not limited to Browserify. It could also be a great way of making it easy to share code between client and server!

Thanks Paolo, for the tip!