Jquery 对象集合的迭代扩展forEach

if (jQuery && !jQuery.fn.forEach) {
    $(function () {
        (function ($) {
            $.fn.extend({
                forEach: function (predicate) {

                    if (this == null) {
                        throw new TypeError(' this is null or not defined');
                    }

                    // 1. Let O be the result of calling toObject() passing the
                    // |this| value as the argument.
                    var O = Object(this);

                    // 2. If isCallable(predicate) is false, throw a TypeError exception. 
                    if (typeof predicate !== "function") {
                        throw new TypeError(predicate + ' is not a function');
                    }

                    //3 call the jq  original API  for iteror
                    $.each(O, function (index, domEle) {
                        predicate($(domEle));
                    });
                }
            })
        })(jQuery);

    });
}