Отслеживание изменений свойств (IE7+)

gistfile1.js

function WatchPropery(watch_object, property_name, callback){
	var current_value = watch_object[property_name],
		old_ie = document.all && document.querySelector && !document.addEventListener || document.all && !document.querySelector;

	// Setter
	function setFunction(value){
		if(current_value !== value){
			current_value = value;
			callback.call(watch_object, current_value)

			return current_value;
		}
	};

	// Getter
	function getFunction(){
		return current_value;
	};


	// < IE9
	if(old_ie){
		var watch_wrap = document.createElement('div'),
			watch_dom = watch_object;

		function attachChangeEvent(){
			watch_dom[property_name] = getFunction;
			watch_dom[property_name].toString = getFunction;
			watch_dom.attachEvent("onpropertychange", onPropertyChange);
		};

		function onPropertyChange(event) {
			if (event.propertyName === property_name) {

				watch_dom.detachEvent("onpropertychange", onPropertyChange);

				setFunction(watch_dom[property_name]);
				attachChangeEvent();
			}
		};

		if(watch_dom.nodeType === undefined){
			watch_dom = document.createElement('WatchPropery');

			for(var read_property in watch_object){
				if(Object.prototype.hasOwnProperty.call(watch_object, read_property)){
					watch_dom[read_property] = watch_object[read_property];
				}
			}
		}


		watch_wrap.appendChild(watch_dom);
		attachChangeEvent();
		watch_wrap.removeChild(watch_dom);

		return watch_dom;
	}

	// > IE9, Chrome, Firefox > 3, Opera > 12
	if(Object.defineProperty){
		Object.defineProperty(watch_object, property_name, {
			get: getFunction,
			set: setFunction
		});

		return watch_object;
	}

	// Opera 10-12, Firefox 3
	if(typeof {}.__defineGetter__ === 'function'){
		watch_object.__defineGetter__(property_name, getFunction);
		watch_object.__defineSetter__(property_name, setFunction);

		return watch_object;
	}

};