A simple approach for handling the dom-ready event

This script is a simple, lazy and hacky replacement for dealing with the dom-ready event (DOMContentLoaded and friends). Basically, it relies on DOM parsing and script execution order by simply putting a script tag at the very end of the document and having it call a list of registered callbacks.

Because of the way the DOM rendering process works, we can guarantee that by the time that script gets executed the DOM is fully ready for use.

Usage

Add the onready.js as the last script in your page, either by embedding it directly (i.e., <script src="onready.js"></script> right before </body>) or by concatenating it to the end of your other scripts during the build process (and making sure that the entire bundle is also embedded right before </body>).

Once the script is loaded, it'll look for a global array named onready with a list of functions to execute. It'll then overwrite that array with a new object that has a replacement push(fn) method that immediately calls any new callbacks that attempts to register themselves after the page has loaded.

To register a new callback with JavaScript, use:

(window.onready=window.onready||[]).push(function(){
  ...
})

To register a new callback with CoffeeScript, use:

(window.onready?=[]).push ->
  ...

Or, if you're in the top-level block and know that this is set to the global object, you can also use:

(@onready?=[]).push ->
  ...

Why?

Advantages:

• Extremely lightweight (4 lines of code).
• Cross browser without the complexity of supporting the various dom ready events and detection techniques.
• No need to load a library prior to registering callbacks.
• The callbacks are triggered at the very earliest moment the DOM is known to be ready.

Disadvantages:

• Ugly syntax. (though, you could do something like window.onready=window.onready||[];function $(fn){onready.push(fn)} at some early point to get a jQuery-like syntax.)

• The onready.js script must be always maintained as the last script to load, which might complicate some workflows.