<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>www.jb51.net JS碰撞检测</title>
<style>
div{100px;
height:100px;
}
#box{background:red; position:absolute; }
#box1{background:green;position:absolute;top:300px; left:300px;}
</style>
<script>
//两个碰撞的盒子。是建立在一个不动的基础上。所以可以根据不动的盒子求出四个方向的left和top值。然后再判断其是否碰撞，且碰撞的过程随时改变其层级，（原需 var 8个变量，现在只需4个变量）
function collText(obj,left,top,obj1){
var l1=obj.offsetLeft-obj.offsetWidth;
var t1=obj.offsetTop-obj.offsetHeight;
var r1=obj.offsetLeft+obj.offsetWidth;
var b1=obj.offsetTop+obj.offsetHeight;
if(left<l1||top<t1||left>r1||top>b1){
obj.style.zIndex=3;
obj1.style.zIndex=1;
return true;
}else{
obj.style.zIndex=1;
obj1.style.zIndex=3;
return false;
}
};
window.onload=function(){
var oBox=document.getElementById('box');
var oBox1=document.getElementById('box1');
oBox.onmousedown=function(ev){
var oEvent= ev || event;
var disX=oEvent.clientX-oBox.offsetLeft;
var disY=oEvent.clientY-oBox.offsetTop;
document.onmousemove=function(ev){
var oEvent= ev || event;
var l=oEvent.clientX-disX;
var t=oEvent.clientY-disY;
oBox.style.left=l+'px' ;
oBox.style.top=t+'px' ;
if(collText(oBox1,l,t,oBox)){
oBox1.style.background='green';
}else{
oBox1.style.background='yellow';
}
};
document.onmouseup=function(){
document.onmousemove=null;
document.onmouseup=null;
oBox.reseaseCapture&&oBox.reseaseCapture();
};
oBox.setCapture&&oBox.setCapture();
return false;
}
oBox1.onmousedown=function(ev){
var oEvent= ev || event;
var disX1=oEvent.clientX-oBox1.offsetLeft;
var disY1=oEvent.clientY-oBox1.offsetTop;
document.onmousemove=function(ev){
var oEvent= ev || event;
var le=oEvent.clientX-disX1;
var to=oEvent.clientY-disY1;
oBox1.style.left=le+'px' ;
oBox1.style.top=to+'px' ;
if(collText(oBox,le,to,oBox1)){
oBox.style.background='red';
}else{
oBox.style.background='#000';
}
};
document.onmouseup=function(){
document.onmousemove=null;
document.onmouseup=null;
oBox1.reseaseCapture&&oBox1.reseaseCapture();
}
oBox1.setCapture&&oBox1.setCapture();
return false;
}
}
</script>
</head>
<body>
<div id="box"></div>
<div id="box1"></div>
</body>
</html>