JavaScript实现点击按钮生成随机颜色可拖动方块

<!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>www.jb51.net JS点击生成随机颜色块</title>
<style type="text/css">
div{
  width: 100px;
  height: 100px;
  background-color: red;
  position: absolute;
  margin-left: 10px;
  float: left;
}
</style>
</head>
<body id="body1">
<button onclick="btn()">创建div</button>
<script>
  function btn(){
    var id;
    //动态创建元素
    var str=document.createElement("div");
    //元素的背景色随机的
    str.style.backgroundColor=getColorRandom();
    //将生成的div追加到body中
    document.getElementById("body1").appendChild(str);
    //随机生成的id设置为动态创建的div的id
    str.id="items"+parseInt(Math.random()*10000);
    // 获取动态生成的div的id
    var obj=document.getElementById(str.id);
    var disX=0;
    var disY=0;
    //鼠标点击落下事件
    obj.onmousedown=function (event){
      disX=event.clientX-obj.offsetLeft;
      disY=event.clientY-obj.offsetTop;
      //鼠标移开事件
      document.onmousemove=function(ev){
        obj.style.left=ev.clientX-disX+"px";
        obj.style.top=ev.clientY-disY+"px";
      }
      //鼠标松开事件
      document.onmouseup= function () {
        document.onmousemove=null;
        document.onmouseup=null;
      }
    }
    //生成随机颜色
    function getColorRandom(){
      var c="#";
      var cArray=["0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"];
      for(var i=0;i<6;i++){
       var cIndex= Math.round(Math.random()*15);
        c+=cArray[cIndex];
      }
      return c;
    }
  }
</script>
</body>
</html>