jquery学习 (3)文本框获取焦点之后变换样式

<!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" />
<title></title>
<style type="text/css"> body{
font:normal 12px/17px Arial;
}
div{
padding:2px;
}
input, textarea {
width: 12em;
border: 1px solid #888;
}
.focus {
border: 1px solid #f00;
background: #fcc;
} </style>
<!-- 引入jQuery -->
<script src="../../scripts/jquery.js" type="text/javascript"></script>
<script type="text/javascript">
$(function(){
$(":input").focus(function(){
$(this).addClass("focus");
if($(this).val() ==this.defaultValue){
$(this).val(""); //获取焦点之后判断是不是更改值
}
}).blur(function(){
$(this).removeClass("focus");
if ($(this).val() == '') {
$(this).val(this.defaultValue);
}
});
})
</script> </head>
<body>
<form action="" method="post" id="regForm">
<fieldset>
<legend>个人基本信息</legend>
<div>
<label for="username">名称:</label>
<input id="username" type="text" value="名称" />
</div>
<div>
<label for="pass">密码:</label>
<input id="pass" type="password" value="密码" />
</div>
<div>
<label for="msg">详细信息:</label>
<textarea id="msg" rows="2" cols="20">详细信息</textarea>
</div>
</fieldset>
</form>
</body>
</html>
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