example.js

// public/javascripts/example.js

ExampleBehavior = Behavior.create({
 initialize : function() {
   this.something = 5;
 },
 onclick : function() {
   this.element.hide();
   // ... more stuff
 },
 onmouseover : function() {
   this.element.setStyle({ backgroundColor : 'red' })
 }, 
 onmouseout : function() {
   this.element.setStyle({ backgroundColor : 'gray' })
 }
})

document.observe('ready', function(){
  Event.addBehavior({
    'div.example' : ExampleBehavior
  })
})