css-functions伪类选择器系列二-EW帮帮网

概述

本文主要讲述CSS的部分伪类选择器第二篇，包括：:nth-child、:nth-last-child、:nth-of-type和:nth-last-of-type。

`:nth-child()`

:nth-child伪类是根据父元素的子元素列表中的索引来选择元素。

语法

:nth-child是以一个参数nth来描述匹配兄弟元素列表中元素索引的模式。元素索引从1开始。

:nth-child(nth) {
  /** */
}

其中nth可以是关键字也可以是函数符号

关键字 ：odd表示奇数，如 1、3、5…；even表示偶数，如 2、4、6。
函数符号
- <An+B>：A表示步长；B表示偏移量；n表示从 0 开始的整数，如 5n+1就是包含 1、6、11…
- nth of <selector>：表示选择与<selector>选择器匹配的第nth个元素，这时的nth可以是<An+B>的模式或者非负整数
非负整数：<nth>也可以就是一个数值，如 1，3，6，8…

示例

效果
代码如下：

<style>
  .first {
    .children.pre span:nth-child(-n + 3) {
      background: rgb(30, 120, 223);
    }

    .children.odd span:nth-child(odd) {
      background: red;
    }

    .children.odd span:nth-child(2n + 1) {
      border: 2px solid #000;
    }

    .children.even span:nth-child(even) {
      background: orange;
    }

    .children.even span:nth-child(2n) {
      border: 4px dotted green;
    }

    .children span:nth-child(-n + 3 of .im) {
      background-color: gold;
    }
  }
</style>
<div class="order">
  <h2><code>:nth-child</code></h2>
  <div class="content first">
    <div class="item">
      <div class="children">
        <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
        <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
      </div>
    </div>
    <div class="item">
      <h5>-n+3:前3个背景为蓝色</h5>
      <div class="children pre">
        <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
        <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
      </div>
    </div>
    <div class="item">
      <h5>odd:背景为红色;2n+1：边框加粗且颜色为黑色</h5>
      <div class="children odd">
        <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
        <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
      </div>
    </div>
    <div class="item">
      <h5>odd:背景为橘色;2n+1：边框改为虚线加粗且颜色为绿色</h5>
      <div class="children even">
        <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
        <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
      </div>
    </div>
    <div class="item">
      <h5>of &lt;selector /&gt; ：子元素前3个`im`类的背景色改为金色</h5>
      <div class="children of">
        <span>1</span><span class="im">2</span><span>3</span><span>4</span
        ><span class="im">5</span> <span class="im">6</span><span>7</span
        ><span>8</span><span class="im">9</span><span>10</span>
      </div>
    </div>
  </div>
</div>

`:nth-last-child()`

:nth-last-child()和:nth-child的语法类似，不过:nth-last-child()是从最后倒着计数，和后者相反。

示例

效果
代码如下：

<style>
  .last {
    .children.pre span:nth-last-child(-n + 3) {
      background: rgb(30, 120, 223);
    }

    .children.odd span:nth-last-child(odd) {
      background: red;
    }

    .children.odd span:nth-last-child(2n + 1) {
      border: 2px solid #000;
    }

    .children.even span:nth-last-child(even) {
      background: orange;
    }

    .children.even span:nth-last-child(2n) {
      border: 4px dotted green;
    }

    .children span:nth-last-child(-n + 3 of .im) {
      background-color: gold;
    }
  }
</style>
<h2><code>:nth-last-child</code></h2>
<div class="content last">
  <div class="item">
    <div class="children">
      <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
      <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>-n+3:后3个背景为蓝色</h5>
    <div class="children pre">
      <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
      <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>odd:背景为红色;2n+1：边框加粗且颜色为黑色</h5>
    <div class="children odd">
      <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
      <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>odd:背景为橘色;2n+1：边框改为虚线且颜色为绿色</h5>
    <div class="children even">
      <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
      <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>of &lt;selector /&gt; ：子元素后3个`im`类的背景色改为金色</h5>
    <div class="children of">
      <span>1</span><span class="im">2</span><span>3</span><span>4</span
      ><span class="im">5</span> <span class="im">6</span><span>7</span
      ><span>8</span><span class="im">9</span><span>10</span>
    </div>
  </div>
</div>

`:nth-of-type()`

:nth-of-type()伪类是基于相同类型（标签名称）的兄弟元素中的位置来匹配元素。

语法

:nth-of-type(nth) {
  /** */
}

nth表示匹配元素的模式，同上差不多。可以是关键词odd或even，也可以是<An+B>，还可以是非负整数。

示例

效果
代码如下：

<style>
  .first {
    .children.odd span.light:nth-of-type(odd) {
      color: red;
    }

    .children.even span.light:nth-of-type(even) {
      color: rgb(99, 32, 32);
      font-weight: bolder;
    }

    .children.blue span:nth-of-type(2n + 1) {
      color: rgb(14, 53, 224);
      font-weight: bolder;
    }
  }
</style>
<h2><code>:nth-of-type</code></h2>
<div class="content first">
  <div class="item">
    <div class="children">
      <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
      <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>odd:颜色为红色</h5>
    <div class="children odd">
      <span>1</span>
      <span class="light">2</span>
      <span>3</span>
      <span class="dark">4</span>
      <span>5</span>
      <span class="light">6</span>
      <span class="light">7</span>
      <span>8</span>
      <span class="light">9</span>
      <span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>even:颜色为棕色</h5>
    <div class="children even">
      <span>1</span>
      <span class="light">2</span>
      <span>3</span>
      <span class="dark">4</span>
      <span>5</span>
      <span class="light">6</span>
      <span class="light">7</span>
      <span>8</span>
      <span class="light">9</span>
      <span>10</span>
    </div>
  </div>

  <div class="item">
    <h5>2n+1:颜色为蓝色</h5>
    <div class="children blue">
      <span>1</span>
      <span class="light">2</span>
      <span>3</span>
      <span class="dark">4</span>
      <span>5</span>
      <span class="light">6</span>
      <span class="light">7</span>
      <span>8</span>
      <span class="light">9</span>
      <span>10</span>
    </div>
  </div>
</div>

`:nth-last-of-type()`

:nth-last-of-type()和:nth-of-type的语法类似，不过:nth-last-of-type()是从最后倒着计数，和后者相反。

示例

效果
代码如下：

<style>
  .last {
    .children.odd span.light:nth-last-of-type(odd) {
      color: red;
    }

    .children.even span.light:nth-last-of-type(even) {
      color: rgb(99, 32, 32);
      font-weight: bolder;
    }

    .children.blue span:nth-last-of-type(2n + 1) {
      color: rgb(14, 53, 224);
      font-weight: bolder;
    }
  }
</style>
<h2><code>:nth-of-last-type</code></h2>
<div class="content last">
  <div class="item">
    <div class="children">
      <span>1</span><span>2</span><span>3</span><span>4</span><span>5</span>
      <span>6</span><span>7</span><span>8</span><span>9</span><span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>odd:颜色为红色</h5>
    <div class="children odd">
      <span>1</span>
      <span class="light">2</span>
      <span>3</span>
      <span class="dark">4</span>
      <span>5</span>
      <span class="light">6</span>
      <span class="light">7</span>
      <span>8</span>
      <span class="light">9</span>
      <span>10</span>
    </div>
  </div>
  <div class="item">
    <h5>even:颜色为棕色</h5>
    <div class="children even">
      <span>1</span>
      <span class="light">2</span>
      <span>3</span>
      <span class="dark">4</span>
      <span>5</span>
      <span class="light">6</span>
      <span class="light">7</span>
      <span>8</span>
      <span class="light">9</span>
      <span>10</span>
    </div>
  </div>

  <div class="item">
    <h5>2n+1:颜色为蓝色</h5>
    <div class="children blue">
      <span>1</span>
      <span class="light">2</span>
      <span>3</span>
      <span class="dark">4</span>
      <span>5</span>
      <span class="light">6</span>
      <span class="light">7</span>
      <span>8</span>
      <span class="light">9</span>
      <span>10</span>
    </div>
  </div>
</div>

css-functions伪类选择器系列二

概述

`:nth-child()`

语法

示例

`:nth-last-child()`

示例

`:nth-of-type()`

语法

示例

`:nth-last-of-type()`

示例

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