<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.box {width: 100px;height: 100px;background: #ccc;position: absolute;left: 0;top: 0;}
</style>
</head>
<body>
<div class="box"></div>
</body>
<script>
var obox = document.querySelector(".box");
//取到事件源的实际宽高
var h = obox.offsetHeight;
var w = obox.offsetWidth;
// 取到可视页面的宽高
var clientHeight = document.documentElement.clientHeight;
var clientWidth = document.documentElement.clientWidth;
obox.onmousedown = function(eve){
// 鼠标点击时的解决兼容问题
var e1 = eve || window.event;
document.onmousemove = function(eve){
// 鼠标滑动时解决兼容
var e = eve || window.event;
var t = e.clientY - e1.offsetY;
var l = e.clientX- e1.offsetX ;
// 通过判断div移动是否超出可视页面
if(t<0){
t=0;
}
if(l<0){
l=0;
}
if(t>clientHeight-h){
t = clientHeight-h;
}
if(l>clientWidth-w){
l=clientWidth-w
}
// 给div设置移动的位置
obox.style.top = t +"px";
obox.style.left = l +"px";
}
// 鼠标相对于网页抬起时删除移动时间
document.onmouseup = function(){
document.onmousemove = null;
}
}
</script>
</html>
