作用：:empty 选择器选取空的元素。空元素指的是不包含子元素或文本的元素。直线电机滑台
语法：$(":empty")
<html>
<head>
<script type="text/javascript" src="http://apps.bdimg.com/libs/jquery/2.1.1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$(":empty").css("background-color","#B2E0FF");
});
</script>
</head>
<body>
<html>
<body>
<h1>Welcome to My Web Page</h1>
<table>
<tr>
<th>Id</th>
<th>LastName</th>
<th>FirstName</th>
<th>Address</th>
<th>City</th>
</tr>
<tr>
<td>1</td>
<td></td>
<td>John</td>
<td>Oxford Street</td>
<td></td>
</tr>
<tr>
<td>2</td>
<td>Bush</td>
<td>George</td>
<td></td>
<td>New York</td>
</tr>
<tr>
<td>3</td>
<td>Carter</td>
<td>Thomas</td>
<td>Changan Street</td>
<td>Beijing</td>
</tr>
<tr>
<td>4</td>
<td>Obama</td>
<td></td>
<td>Pennsylvania Avenue</td>
<td>Washington</td>
</tr>
</table>
</body>
</html>
</body>
</html>
原文：https://www.cnblogs.com/furuihua/p/11942060.html