JavaScript链式编程模拟Jquery函数

 <span>Hello,World！</span>
 <script type="text/javascript">
     Jq = function (tagName) {
         var tagArr = document.getElementsByTagName(tagName);
         var ret = {
             tag: tagArr,
             css: function (attribute, value) {
                 for (var i = ; i < this.tag.length; i++) {
                     this.tag[i].style[attribute] = value;
                 }
                 return this;
             }
         }
         return ret;
     }

     window.onload = function () {
         Jq("span").css("color", "red")
                   .css("border", "1px solid green")
                   .css("padding", "10px");
     }
 </script>