JavaScript 实现简单拖拽效果

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>javascript拖拽</title>
<style>
.test{
 text-align:center;
 width:300px;
 height:30px;
 line-height:30px;
 background:#f60;
 position:absolute;
}
.test:hover{
 cursor:move;
}
</style>
</head>
<body>
<script src="jquery-1.6.2.min.js"></script>
<div class="test">jb51拖拽测试</div>
<br/><br/>
<h1>如果无效请刷新下页面..</h1>
<script>
;$(function(){
 var isMove=false;
 $(".test").mousedown(function(){isMove=true;}).mouseup(function(){isMove=false;});
 $(document).mousemove(function(e){
  if(!isMove){return;};
  var X=e.clientX-parseInt($(".test").width()/2);
  var Y=e.clientY-parseInt($(".test").height()/2);
  $(".test").css({"left":X,"top":Y,"cursor":"move"});
 });
});
</script>
</body>
</html>