<script type="text/javascript">  
    function openWindow(){
       var a=confrim("open or not");
       if(a==true){
           var b=prompt("open or not","http://www.imooc.com");
       }
       else{
           return;
       }
       if(b !=null){
           window.open(b,'_blank','windth=400,height=500,menubar=no,toolbar=no')
       }
       else{
           return;
       }
        }

    
    
  </script>