Front End Collision

Blog of software engineer Josh Beam

Lightweight dependency modularization

22 March 2015 — Josh Beam — javascript

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So what's this post all about? We're going to examine an interesting alternative for passing dependencies between JavaScript modules. The goal is to avoid any overhead (by using libraries like RequireJS), but also to avoid attaching too many things to the global namespace...

A common approach

A common approach when utilizing the module pattern or something close to it, is to attach the end object to the window, or return the object inside some sort of local variable to create a namespace for your module.

So you might end up having something like this:

// first.module.js
;(function(win) {
	var exports = //code

	win.firstModule = exports;

// several more modules...

// and eventually a module that depends on firstModule

// fifth.module.js
;(function(win,firstModule) {
	// do something with firstModule

	var exports = //code;

	win.fifthModule = exports;
<!-- then in your html... -->

<script src="first.module.js"></script>
<!-- several other modules -->
<scirpt src="fifth.module.js"></script>

Of course, the obvious problems with this are:

  1. You attach a lot of stuff to the global scope (this can be overcome with various techniques, though)
  2. You have to get the order of your <script> tags pretty exact (we’re pretending we’re not using a task runner here, like gulp)

… and probably several other I’m forgetting about. There are other ways to do this (a popular library like RequireJS, for example), but in my case, I wanted to try to use a basic object that would be attached to the window, and have all of my dependencies attach to that global object.

A global dependencies object

For angular-state-manager, I utilized a global object called stateManagerDependencies, or something along that line, to attach all of my modules to that would eventually go into the main stateManager module.

The purpose of this was to only have one object (the stateManagerDependencies object) be attached to the global scope (i.e. window object), and that would hold all of the dependencies, as opposed to attaching each dependency to the global scope at the end of each module.

// dependencies.js
;(function(win) {

	win.stateManagerDependencies = {};


// first.example.module.js
;(function(dependencies) {
	var dependencies = dependencies;

	// then, use them...

// etc.

Obvious downsides to this approach

  1. You’re still attaching some strangely named global object to the window
  2. In each module that depends on the dependencies object, there is no error-checking or method to list what modules are available inside the dependencies object (a possible fix for this is to simply implement some of those methods, for example: .list(), or .checkFor(), etc.)