<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>点击将DIV变成红色</title>
<style>
body{font:12px/1.5 Tahoma;text-align:center;}
code,input,button{font-family:inherit;}
#div{width: 1000px;height: 240px;position: relative;}
#div div{width: 200px;height: 200px;background-color: black;position: relative;float: left;margin: 10px;}
button{cursor:pointer;}
</style>
<script>
window.onload = function(){
var oDiv = document.getElementById("div").getElementsByTagName("div");
var oButton = document.getElementsByTagName("button")[0];
oButton.onclick = function(){
for(var i = 0;i<oDiv.length;i++){
oDiv[i].style.backgroundColor = "red";
}
};
};
</script>
</head>
<body>
<div id="div">
<div></div>
<div></div>
<div></div>
</div>
<p><button>点击将DIV变成红色</button></p>
</body>
</html>