Element.Event.change.js

/*
---

name: Element.Event.Change

description: Normalizes the onchange-event in Internet Explorer for checkboxes and radio buttons.

license: MIT-style license.

requires: [Element.Event]

provides: Element.Event.Change

...
*/

/*<ltIE9>*/
if (!window.addEventListener) (function(){

var getValue = function(element){
	var type = element.type;
	return element[type == 'radio' || type == 'checkbox' ? 'checked' : 'value'];
};

var hasChanged = function(event){
	var target = event.target,
		value = target.retrieve('$change').value;
	if (value == null || value == getValue(target)) return false;
	switch (event.key){
		case 'up': case 'down': case 'left': case 'right': return target.type == 'radio';
		case 'space': return target.type == 'checkbox';
	}	
}

Element.Events.change = {

	base: function(){
		var type = this.type;
		return (type == 'checkbox' || type == 'radio') ? 'click' : 'change';
	},

	condition: function(event){
		return (event.target.type == 'radio' ? (event.type == 'keyup' ? !target.checked : target.checked) : true);
	},

	onAdd: function(fn){
		var update = function(event){
			event.target.store('$change', {
				type: event.type,
				value: getValue(event.target)
			});
		};
		this.addEvents(this.retrieve('$changeEvents', {
			keyup: function(event){
				if (hasChanged(event)) fn.call(this, event);
			},
			focus: update,
			keydown: update
		});
	},

	onRemove: function(){
		this.removeEvents(this.retrieve('$changeEvents')).eliminate('$changeEvents');
	}

};

})();
/*</ltIE9>*/