--- title: ':first-child' slug: 'Web/CSS/:first-child' translation_of: 'Web/CSS/:first-child' ---
{{CSSRef}}

: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

{{csssyntax}}

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

{{EmbedLiveSample('Basic_example', 500, 200)}}

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

{{EmbedLiveSample('Styling_a_list')}}

Specifications

Specification Status Comment
{{SpecName('CSS4 Selectors', '#first-child-pseudo', ':first-child')}} {{Spec2('CSS4 Selectors')}} Matching elements are not required to have a parent.
{{SpecName('CSS3 Selectors', '#first-child-pseudo', ':first-child')}} {{Spec2('CSS3 Selectors')}} No change.
{{SpecName('CSS2.1', 'selector.html#first-child', ':first-child')}} {{Spec2('CSS2.1')}} Initial definition.

浏览器兼容性

{{Compat("css.selectors.first-child")}}

相关链接