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:first-child

:first-child CSS pseudo-class 表示在一组兄弟元素中的第一个元素。

/* Selects any <p> that is the first element
   among its siblings */
p:first-child {
  color: lime;
}

Note: 最初定义时，所选元素必须有一个parent。而从选择器 Level 4 开始，parent不再是必须的。

语法

:first-child

示例

Basic example

HTML

<div>
  <p>This text is selected!</p>
  <p>This text isn't selected.</p>
</div>

<div>
  <h2>This text isn't selected: it's not a `p`.</h2>
  <p>This text isn't selected.</p>
</div>

CSS

p:first-child {
  color: lime;
  background-color: black;
  padding: 5px;
}

Result

Styling a list

HTML

<ul>
  <li>Item 1</li>
  <li>Item 2</li>
  <li>Item 3
    <ul>
      <li>Item 3.1</li>
      <li>Item 3.2</li>
      <li>Item 3.3</li>
    </ul>
  </li>
</ul>

CSS

ul li {
  color: blue;
}

ul li:first-child {
  color: red;
  font-weight: bold;
}

Result

Specifications

Specification Status Comment
Selectors Level 4
:first-child		 Working Draft Matching elements are not required to have a parent.
Selectors Level 3
:first-child		 Recommendation No change.
CSS Level 2 (Revision 1)
:first-child		 Recommendation Initial definition.

浏览器兼容性

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相关链接