watch

watch.js

;(function() {
	'use strict';

	if (!Object.prototype.watch) {
		Object.defineProperty(Object.prototype, 'watch', {
			enumerable: false,
			configurable: true,
			writable: false,
			value: function (prop, handler) {
				var oldval = this[prop];
				var newval = oldval;

				var getter = function () {
					return newval;
				};

				var setter = function (val) {
					oldval = newval;

					return (newval = handler.call(this, prop, oldval, val));
				};

				if (delete this[prop]) { // can't watch constants
					Object.defineProperty(this, prop, {
						get: getter,
						set: setter,
						enumerable: true,
						configurable: true
					});
				}
			}
		});
	}
	 
	if (!Object.prototype.unwatch) {
		Object.defineProperty(Object.prototype, 'unwatch', {
			enumerable: false,
			configurable: true,
			writable: false,
			value: function (prop) {
				var val = this[prop];

				delete this[prop]; // remove accessors

				this[prop] = val;
			}
		});
	}
})();