<!doctype html>
<html>
<head>
<meta content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0" name="viewport">
<meta charset="utf-8">
<title></title>
<style>
.hover{
width:100px;
height:100px;
background:red;
float:left;
}
.hovers{
width:100px;
height:100px;
background:yellow;
float:left;
}
</style>
</head>
<body>
<input type="button" value="增">
<!-- 增 -->
<input type="button" value="删">
<!-- 删 -->
<input type="button" value="改">
<!-- 查 -->
<div id="main"></div>
<!-- 元素库 -->
</body>
</html>
<script>
var ints = document.getElementsByTagName('input');
for(var i = 0 ; i<ints.length ; i++){
ints[i].index = i ;
ints[i].onclick=function(){
if(this.index==0){
var odiv = document.createElement('div');
odiv.setAttribute('class','hover')
document.getElementById('main').appendChild(odiv);
}
else if(this.index==1){
var odiv = document.getElementById('main');
var odivs = odiv.getElementsByTagName('div');
if(odivs.length==0){
alert('没有了');
}
else{
document.getElementById('main').removeChild(odivs[odivs.length-1]);
}
}
else if(this.index==2){
var odiv = document.getElementById('main');
var odivs = odiv.getElementsByTagName('div');
for(var i = 0 ;i<odivs.length;i++){
odivs[i].setAttribute('class','hovers')
}
}
}
}
</script>
