<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1">
<title></title>
<style type="text/css">
#box{
width: 300px;
height: 300px;
background: gray;
position: absolute;
left: 0;
top: 0;
}
#header{
width: 100%;
height: 50px;
background: black;
position: absolute;
left: 0;
top: 0;
}
#header span{
width: 50px;
height: 50px;
background: yellow;
color: black;
position: absolute;
right: 0;
}
</style>
</head>
<body>
<div id="box">
<div id="header">
<span>B</span>
</div>
</div>
<script type="text/javascript">
var oDiv = document.getElementById("box");
var oSpan = document.querySelector('#header span');
var arr = [];
oDiv.onmousedown = function(evt){
//获取事件对象的兼容
var e = evt || window.event;
//获取事件源的兼容
var target = e.target || e.srcElement;
//事件委托
if(target.id == 'header'){
//鼠标相对于事件源元素的x、y坐标
var disX = e.offsetX;
var disY = e.offsetY;
//#box初始位置
arr.push({"left" : oDiv.offsetLeft,"top" : oDiv.offsetTop});
//鼠标移动事件
document.onmousemove = function(evt){
var e = evt || window.event;
var oHtml = document.documentElement;
var left = e.pageX - disX;
var top = e.pageY - disY;
//控制#box不脱离浏览器边框
if(left <= 0){
left = 0
}else if(left >= oHtml.clientWidth - oDiv.offsetWidth){
left = oHtml.clientWidth - oDiv.offsetWidth
}
if(top <= 0){
top = 0;
}else if(top >= oHtml.clientHeight - oDiv.offsetHeight){
top = oHtml.clientHeight - oDiv.offsetHeight;
}
oDiv.style.left = left + 'px';
oDiv.style.top = top + 'px';
//随时记录#box坐标,用于原路返回
arr.push({"left" : oDiv.offsetLeft,"top" : oDiv.offsetTop});
}
//鼠标松开事件
document.onmouseup = function(){
document.onmousemove = null;
}
//禁止鼠标拖动
document.ondragstart = function(){
return false;
}
}
}
//span元素新增监听事件,将#box原路返回
oSpan.addEventListener("click",function(){
var index = arr.length - 1;
var timer = setInterval(function(){
if(index == -1){
clearInterval(timer);
arr = [];
}else{
oDiv.style.left = arr[index].left + 'px';
oDiv.style.top = arr[index].top + 'px';
index --;
}
},20)
},false);
</script>
</body>
</html>
