<!DOCTYPE HTML>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
#box {width:100px; height:100px; background:red;position:absolute;}
</style>
</head>
<body>
<div id="box">
</div>
<script type="text/javascript">
var box = document.getElementById('box');
//定义全局变量
var divX = 0; //div的x坐标
var divY = 0; //div的y坐标
var mouseX = 0; //鼠标的x坐标
var mouseY = 0; //属性的y坐标
var sw = false; //表示开关
//绑定mouserdown事件
box.onmousedown = function(evt){
var e = evt || window.event;
console.log(e);
//获取div的位置
divX = this.offsetLeft; //值是没有单位的
divY = this.offsetTop;
//获取鼠标所处的位置
mouseX = e.clientX;
mouseY = e.clientY;
//开启开关
sw = true;
}
//绑定mousemove事件
document.onmousemove = function(evt){
var e = evt || window.event;
//只有开启了开关，才有效
if (sw) {
var disX = e.clientX - mouseX;
var disY = e.clientY - mouseY;
//console.log(disX,disY);
//利用相对论，设置div的left和top值就可以了
box.style.left = divX + disX + "px"; //注意加单位
box.style.top = divY + disY + "px";
}
}
//绑定mouseup事件
document.onmouseup = function(){
sw = false;
}
</script>
</body>
</html>
