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());