function aa(b) {
        var a = 12;
        function bb() {
            alert(a);
            alert(b);
        }
        return bb;
      }
    var cc = aa(24);
   //封闭函数写闭包 
   /*var cc =(function (b) {
         var a = 12;
          function bb() {
             alert(a);
            alert(b);
        }
        return bb;
   })(24);*/
    cc()

索引值

li{
        height: 30px;
        background-color: gold;
        margin-bottom: 10px;
    }
</style>
<script type="text/javascript">
    window.onload = function () {
        var ali = document.getElementsByTagName('li');
    
        for(var i=0; i<ali.length; i++){
            (function (i) {
                ali[i].onclick = function () {
                    alert(i)
                }
            })(i)
        }
   }