<!DOCTYPE html>
<html>
<head>
<title>element选择器</title>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js" type="text/javascript"></script>
</head>
<body>
<button id="btntest">点我</button>
</body>
<script type="text/javascript">
$("button").attr("disabled","true");
</script>
</html>
为什么没有变灰？
