Table of Contents
HTML代码
第2个元素
CSS选择器
总结
Home Web Front-end HTML Tutorial CSS3中:first-child和:first-of-child的区别_html/css_WEB-ITnose

CSS3中:first-child和:first-of-child的区别_html/css_WEB-ITnose

Jun 24, 2016 am 11:36 AM

CSS中加入了很多高级的选择器,能让我们方便的查找到元素,然后给查找到的元素设置样式,其中:first-child和:first-of-child看似只相差一个单词,但是却有不同的用法和意义,今天的这篇文章就给大家来说说:first-child和:first-of-child两个选择器的区别。

HTML代码

加入我们有这样的一段HTML代码:

<div>    <p>第1个元素</p>    <h1 id="第-个元素">第2个元素</h1>    <span>第3个元素</span>    <span>第4个元素</span></div>
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CSS选择器

我们要查找其中的元素,如果使用下面的定义方法

p:first-child  匹配到的是p元素,因为p元素是div的第一个子元素; h1:first-child  匹配不到任何元素,因为在这里h1是div的第二个子元素,而不是第一个; span:first-child  匹配不到任何元素,因为在这里两个span元素都不是div的第一个子元素; :first-child  匹配到的是p元素,因为在这里div的第一个子元素就是p。

上面应用的样式,有两个是匹配不到的,但是别慌张,CSS中还定义了:first-of-child伪类,请看他的用法和讲解:

p:first-of-type  匹配到的是p元素,因为p是div的所有为p的子元素中的第一个,事实上这里也只有一个为p的子元素; h1:first-of-type  匹配到的是h1元素,因为h1是div的所有为h1的子元素中的第一个,事实上这里也只有一个为h1的子元素; span:first-of-type  匹配到的是第三个子元素span。这里div有两个为span的子元素,匹配到的是第一个。 :first-of-type  匹配到的是p元素

总结

:first-child 匹配的是某父元素的第一个子元素,可以说是结构上的第一个子元素。 :first-of-type 匹配的是该类型的第一个,类型是指什么呢,就是冒号前面匹配到的东西,比如 p:first-of-type,就是指所有p元素中的第一个。这里不再限制是第一个子元素了,只要是该类型元素的第一个就行了,当然这些元素的范围都是 属于同一级的,也就是同辈的。

同样类型的选择器 :last-child  和 :last-of-type、:nth-child(n)  和  :nth-of-type(n) 也可以这样去理解。

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