Developing Unobtrusive JavaScript with MooTools.

application.js

var Application = {

  init: function(){

    if (Browser.Engine.trident) Application.fixIE();
      
    if ($('form-entry')) Application.initFormEntry();

    if ($$('a.hover-me').length > 0) Application.initHoverEffects();

  },

  start: function(){

    if ($$('a.resize-me')) Application.resizeImages();

  },

  fixIE: function(){
     ...
  },

  ...

}

window.addEvent('domready', Application.init);
window.addEvent('load', Application.start);