使用JS写一个用鼠标拖动DIV到任意地方

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
       div{
        width:200px;
        height:200px;
        background:red;
       } 
</style>
</head>
<body>
  <div id="oblong"></div>
</body>
   <script type="text/javascript">
     document.getElementById('oblong').οnmοusedοwn=function(){
      var oblong=document.getElementById("oblong");
      oblong.style.cursor="pointer";
      document.οnmοusemοve=function(){
      var x=event.clientX;
    var y=event.clientY;
       oblong.style.position='fixed';
    oblong.style.left=(x-100)+'px';
    oblong.style.top=(y-100)+'px';
    }
     }
     document.getElementById("oblong").οnmοuseup=function(){


         document.οnmοusemοve=false;
     }
   </script>
</html>