if (!Object.prototype.watch) {
    Object.defineProperty(
        Object.prototype,
        'watch', {
            enumerable: false,
            configurable: true,
            writable: false,
            value: function (prop, handler) {
                var old = this[prop];
                var cur = old;
                var getter = function () {
                    return cur;
                };
                var setter = function (val) {
                    cur = val;
                    handler.call();
                    return cur;
                };
                if (delete this[prop]) {
                    Object.defineProperty(this, prop, {
                        get: getter,
                        set: setter,
                        enumerable: true,
                        configurable: true
                    });
                }
            }
        }
    );
}