<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<title>鼠标拖拽，不能拖出指定对象，吸附作用（类似PS工具框）</title>
<style>
#div1{width: 100px;height: 100px;background: red;position: absolute;}
#div2{width: 700px;height: 500px;background: #ccc;position: relative;margin:100px auto;}
</style>
<script>
window.onload=function(){
var oDiv=document.getElementById('div1');
var oDiv2=document.getElementById('div2');
var disX=0;
var disY=0;
oDiv.onmousedown=function(ev){
var oEvent=ev||event;
disX=oEvent.clientX-oDiv.offsetLeft;
disY=oEvent.clientY-oDiv.offsetTop;
document.onmousemove=function(ev){
var oEvent=ev||event;
var left=oEvent.clientX-disX;
var top=oEvent.clientY-disY;
var right=oDiv2.offsetWidth-oDiv.offsetWidth;
var bottom=oDiv2.offsetHeight-oDiv.offsetHeight;
//让div出不去浏览器
if(left<50){//吸附距离
left=0;
}else if(left>right){
left=right;
}
if(top<50){
top=0;
}else if(top>bottom){
top=bottom;
}
oDiv.style.left=left+'px';
oDiv.style.top=top+'px';
};
document.onmouseup=function(ev){
document.onmousemove=null;
document.onmouseup=null;
};
return false;//火狐阻止默认事件，不然会有bug，解决下面div一定要加内容的bug
}
}
</script>
</head>
<body>
<div id="div2">
<div id="div1"></div>
</div>
</body>
</html>