怎么用JavaScript制作右键菜单,和在网页中移动层

<script>
var div=document.createElement('div'); //全局变量
var tmp=0; //全局变量
document.onclick=function()
{
  div.style.display!='none'?div.style.display='none':div.style.display='';
}
document.oncontextmenu=function()
{
  div.style.position='absolute';
  div.style.backgroundColor='red';
  div.style.display='';
  div.style.width='200px';
  div.style.height='100px';
  div.style.left=event.clientX;
  div.style.top=event.clientY;
  tmp=event.clientY;
  div.innerHTML='menu';  
  document.body.appendChild(div);
  event.returnValue=false;
  event.calcelBubble=true;
}
window.onscroll=function()
{
  div.style.top=(document.body.scrollTop+parseInt(tmp))+'px';
}
</script>
<body>
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</body>