特殊的属性操作，如class，for等
操作class：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
div {
width: 100px;
height: 200px;
border: 1px solid gray;
}
.two {
background: red;
}
</style>
</head>
<body>
<div id="one" class="box"></div>
<form action="">
<label for="uPwd">姓名：</label><input type="text" name="" id="uName">
<label for="uPwd">密码：</label><input type="password" name="" id="uPwd">
</form>
<script type="text/javascript">
var box = document.getElementById("one");
box.className = "two";
</script>
</body>
</html>
操作class时不能直接使用class要使用className进行操作
操作for
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
div {
width: 100px;
height: 200px;
border: 1px solid gray;
}
.two {
background: red;
}
</style>
</head>
<body>
<div id="one" class="box"></div>
<form action="">
<label for="uPwd" id="lab">姓名：</label><input type="text" name="" id="uName">
<label for="uPwd">密码：</label><input type="password" name="" id="uPwd">
</form>
<script type="text/javascript">
var box = document.getElementById("one");
box.className = "two";
var ol = document.getElementById("lab");
ol.htmlFor = "uName";
</script>
</body>
</html>
