<div id="div">
<div> <!-- first level -->
<div> <!-- second level -->
<div>1.1</div> <!-- third level -->
<div>1.2</div>
</div>
<div>
<div></div>
<div>2.2</div>
</div>
</div>
</div>
选择器表达式是jQuery中用于选择元素的语法。以下是选择以下内容所需的jQuery选择器表达式:
1. 选择一级注释的div:$("div:first-child")
2. 选择二级注释的div:$("div:first-child > div:first-child")
3. 选择三级注释的div:$("div:first-child > div:first-child > div:first-child")