withTest2 作用域链 

 <body>
 <div id="alertRet"> </div>

    <script type="text/javascript">
    /*
self.alert=function(str){
    var ret=document.getElementById("alertRet");
    var element=document.createElement("div");
    element.append(str);
    ret.append(element);
};
*/

  function withTest() {
   var userName = "jeff wong";

   //暂时修改作用域链
   with (document) {
    writeln("Hello,");
    writeln(userName);
   }//with内的语句执行完之后，作用域链恢复原状
    
    alert(userName);
  }
  withTest();
    </script>
 </body>

 

posted @ 2018-02-07 17:23  sky20080101  阅读(42)  评论(0)    收藏  举报