<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
*{
padding: 0;
margin: 0;
}
div{
200px;
height: 200px;;
}
#box_1{
background: #919191;
position: absolute;
left: 50%;
top:50%;
margin-left: -50px;
margin-top: -50px;
}
#box_2{
background: blue;
position: absolute;
}
</style>
</head>
<body>
<div id="box_1"></div>
<div id="box_2"></div>
</body>
<script>
//绑定事件
var box2=document.getElementById('box_2');
var box1=document.getElementById('box_1');
document.onmousemove=function(e){
var e= e||event;
box2.style.left= e.clientX-100+'px';
box2.style.top= e.clientY-100+'px';
//box2
var oL=box2.style.left;
var oT=box2.style.top;
//box1
var osT=box1.offsetTop;
var osL=box1.offsetLeft;
//设置碰撞的上下左右
if(parseInt(oL)>osL-200&&parseInt(oL)<osL+200&&parseInt(oT)>osT-200&&parseInt(oT)<osT+200){
box1.style.background='red';
// console.log(1);
}
}
</script>
</html>