出来的框输入网址跳转不对

  function Click()    {         var isClick;        var webS;        isClick=prompt("是否打开？",webS);        if(isClick!=null&&webS==null)        {            window.open("http://www.imooc.com/",'width=400','height=500');             if(webS!=null)             {            window.open(webS);             }        }       else        {            return false;        }    }