jQuery聚合函数实例

(function($) {  $.fn.aggregate = function(seed, func) {    var _r = seed == null ? "" : seed;    this.each(function(index, element) {      _r = func(_r, element);    });    return _r;  };  $.fn.count = function() {    return       this.aggregate( 0, // seed      function(result, _) { // func        return result + 1;      });  };})(jQuery);alert($("a").count());