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648 lines
11 KiB
Markdown
648 lines
11 KiB
Markdown
---
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title: CSS选择器
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createTime: 2022-03-26T11:46:50.024Z
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permalink: /article/8vev8ixl
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author: pengzhanbo
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tags:
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- css
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top: false
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type: null
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---
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## Basic Selectors 基础选择器
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### Element selector
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根据 element type 匹配 一组元素
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``` html
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...
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<style>
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p { color: red; }
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</style>
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...
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<p>content</p>
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...
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```
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### Class selector
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根据 element 声明的 class属性值 匹配一组元素
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``` html
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...
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<style>
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.red { color: red; }
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</style>
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...
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<p class="red">content</p>
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...
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```
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### ID selector
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根据 element 声明的 ID属性值，匹配一个元素（一个页面中，ID具有唯一性）
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``` html
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...
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<style>
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#red { color: red; }
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</style>
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...
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<p id="red">content</p>
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...
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```
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### Universal selector
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通配符，匹配所有 element
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``` html
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...
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<style>
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* { color: red; }
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</style>
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...
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<p>content</p>
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<span>span</span>
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...
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```
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## Attribute Selectors
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### \[attribute\] selector
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匹配声明了该attribute的 一组 element
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``` html
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...
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<style>
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[href] { color: red; }
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</style>
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...
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<a href="">content</a>
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...
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```
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### \[attribute="x"\] selector
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匹配声明了该attribute，且值为 x 的一组 element
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``` html
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...
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<style>
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[title="a"] { color: red; }
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</style>
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...
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<abbr title="a">abbr</abbr>
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...
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```
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### \[attribute~="x"\] selector
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匹配声明了该attribute，且值包含了 单词 x 的一组 element
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``` html
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...
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<style>
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[title~="style"] { color: red; } /* 匹配包含了 独立单词 style 的 element， */
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</style>
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...
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<abbr title="sheet style">abbr</abbr>
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<abbr title="sheetstyle"></abbr> <!-- no match -->
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...
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```
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### \[attribute|="x"\] selector
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匹配声明了该attribute，且值包含了一个 `x-` 开头的连字符拼接的词 的一组 element
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``` html
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...
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<style>
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/* lang的值必须 包含 en 通过连接符 - 连接另一个单词的 词 */
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[lang|="en"] { color: red; }
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</style>
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...
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<abbr lang="en-US">abbr</abbr>
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<!-- no match lang="en" lang="enUS" -->
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...
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```
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### \[attribute^="x"\] selector
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匹配声明了该attribute，且值是以 x 作为开头的 一组 element
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``` html
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...
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<style>
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[href^="https://"] { color: red; }
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</style>
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...
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<a href="https://example.com">content</a>
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...
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```
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### \[attribute$="x"\] selector
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匹配声明了该attribute，且值是以 x 作为结尾的 一组 element
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``` html
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...
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<style>
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[href$=".pdf"] { color: red; }
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</style>
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...
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<a href="https://example.com/a.pdf">content</a>
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...
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```
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### \[attribute*="x"\] selector
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匹配声明了该attribute，且值包含了子串 x 的 一组 element
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``` html
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...
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<style>
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[href*="example"] { color: red; }
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</style>
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...
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<a href="https://example.com">content</a>
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...
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```
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## Combinators 关系选择器
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关系选择器适用于 任意选择器 的组合
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### selector1 selector2 后代关系选择器
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匹配 selector1 的元素中，所有 selector2 的 元素
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``` html
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...
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<style>
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section span { color: red; }
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</style>
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...
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<section>
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<span></span> <!-- match -->
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<p><span></span></p> <!-- match -->
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</section>
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...
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```
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### selector1 > selector2 子代关系选择器
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匹配 selector1 的下一级满足 selector2 的 一组元素
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``` html
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...
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<style>
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section > span { color: red; }
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</style>
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...
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<section>
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<span></span> <!-- match -->
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<p><span></span></p> <!-- no match -->
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</section>
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...
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```
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### selector1 + selector2 相邻兄弟选择器
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匹配selector1后同级的紧跟的selector2的一个元素
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``` html
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...
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<style>
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h2 + p { color: red; }
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</style>
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...
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<p></p> <!-- no match -->
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<h2></h2>
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<p></p> <!-- match -->
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<p></p> <!-- no match -->
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...
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```
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### selector ~ selector2 一般兄弟选择器
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匹配selector1后同级的selector2的一组元素
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``` html
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...
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<style>
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h2 ~ p { color: red; }
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</style>
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...
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<p></p> <!-- no match -->
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<h2></h2>
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<p></p> <!-- match -->
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<p></p> <!-- match -->
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<span></span>
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<p></p> <!-- match -->
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...
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```
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## Group Selectors 组合选择器
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### selector1, selector2, ...
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匹配用`,` 隔开的所有选择器
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``` html
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...
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<style>
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p, span { color: red; }
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</style>
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...
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<section>
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<span></span>
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<p><span></span></p>
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</section>
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...
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```
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## Pseudo-elements 伪元素选择器
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### ::first-letter
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匹配 element中的首个字符（字母、中文字、符号均可）
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``` html
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...
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<style>
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p::first-letter { color: red; }
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</style>
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...
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<p>One</p> <!-- match: O -->
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...
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```
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### ::first-line
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匹配 element中的首行文字
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``` html
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...
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<style>
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p::first-line { color: red; }
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</style>
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...
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<p>
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One Two <br> <!-- match -->
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Three
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</p>
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...
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```
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### ::before
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和 `content` 属性一起使用，在匹配的元素内容之前生成的内容
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``` html
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...
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<style>
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p::before { content: 'before ' }
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</style>
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...
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<p>
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One Two <!-- render: before One Two -->
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</p>
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...
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```
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### ::after
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和 `content` 属性一起使用，在匹配的元素内容之后生成的内容
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``` html
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...
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<style>
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p::after { content: ' after' }
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</style>
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...
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<p>
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One Two <!-- render: One Two after -->
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</p>
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...
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```
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## Pseudo-classes 伪类选择器
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### :link
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匹配一个没有被访问过的链接
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``` html
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...
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<style>
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a:link { color: red }
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</style>
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...
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<a href="">link</a>
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...
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```
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### :visited
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匹配一个已访问过的链接
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``` html
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...
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<style>
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a:visited { color: red }
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</style>
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...
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<a href="">link</a>
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...
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```
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### :active
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匹配一个正在被激活的链接
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``` html
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...
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<style>
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a:active { color: red }
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</style>
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...
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<a href="">link</a>
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...
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```
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### :hover
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匹配一个被光标悬停的链接
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``` html
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...
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<style>
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a:hover { color: red }
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</style>
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...
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<a href="">link</a>
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...
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```
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### :focus
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匹配一个具有焦点的元素
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``` html
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...
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<style>
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input:focus { color: red }
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</style>
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...
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<input type="text">
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...
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```
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### :target
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匹配一个已被链接到的元素。
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例如通过`<a href="#heading"></a>`链接的head元素
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``` html
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...
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<style>
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h2:target { color: red }
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</style>
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...
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<h2 id="heading">heading</h2>
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...
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```
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### :first-child
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匹配在同一个父元素内的的第一个子元素
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``` html
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...
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<style>
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p:first-child { color: red }
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</style>
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...
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<p>first child</p> <!-- match -->
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<p>second child</p>
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...
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```
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### :last-child
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匹配在同一个父元素内的的最后一个子元素
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``` html
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...
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<style>
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p:last-child { color: red }
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</style>
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...
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<p>first child</p>
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<p>last child</p> <!-- match -->
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...
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```
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### :nth-child(n)
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匹配在同一个父元素内的从上往下数的第N子个元素
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``` html
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...
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<style>
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p:nth-child(2) { color: red }
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</style>
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...
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<p>first child</p>
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<p>second child</p> <!-- match -->
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...
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```
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### :nth-last-child(n)
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匹配在同一个父元素内的从下往上数的第N个子元素
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``` html
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...
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<style>
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p:nth-last-child(2) { color: red }
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</style>
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...
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<p>first child</p> <!-- match -->
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<p>second child</p>
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...
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```
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### :first-of-type
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匹配在同一个父元素中的同类型的第一个元素
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``` html
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...
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<style>
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p:first-of-type { color: red }
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</style>
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...
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<p>first child</p> <!-- match -->
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<p>second child</p>
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...
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```
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### :last-of-type
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匹配在同一个父元素中的同类型的最后一个元素
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``` html
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...
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<style>
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p:last-of-type { color: red }
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</style>
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...
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<p>first child</p> <!-- match -->
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<p>second child</p>
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...
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```
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### :nth-of-type(n)
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匹配在同一个父元素中的同类型的从上往下数的第N个元素
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``` html
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...
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<style>
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p:nth-of-type(2) { color: red }
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</style>
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...
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<p>first child</p>
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<p>second child</p> <!-- match -->
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...
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```
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### :nth-last-of-type(n)
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匹配在同一个父元素中的同类型的从下往上数的第N个元素
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``` html
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...
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<style>
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p:nth-last-of-type(2) { color: red }
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</style>
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...
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<p>first child</p> <!-- match -->
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<p>second child</p>
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...
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```
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### :only-child
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如果元素是其父元素的唯一子元素，则匹配该元素
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``` html
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...
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<style>
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section p:only-child { color: red }
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</style>
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...
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<section>
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<p> only child </p>
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</section>
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...
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```
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### :only-type
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如果元素是其父元素的唯一的同类型的子元素，则匹配该元素
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``` html
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...
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<style>
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section p:only-of-type { color: red }
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</style>
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...
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<section>
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<p> only </p> <!-- match -->
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<span></span>
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</section>
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...
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```
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### :lang(lang)
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匹配给定语言的元素
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``` html
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...
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<style>
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div:lang(fr) { color: red }
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</style>
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...
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<section>
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<div lang="fr"><q>This French quote has a <q>nested</q> quote inside.</q></div>
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</section>
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...
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```
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### :empty
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匹配没有子元素或内容的元素
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``` html
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...
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<style>
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div:empty { background-color: red }
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</style>
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...
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<section>
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<div></div>
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</section>
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...
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```
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### :root
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匹配文档的根元素， （即匹配的 `<html>`元素）
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### :enabled
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匹配未被禁用的表单控件元素
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### :disabled
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匹配被禁用的表单控件元素
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### :checked
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匹配选中的单选或复选框类型的输入元素。
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### :not(selector)
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协商伪类。匹配不匹配选择器的元素。
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## 实验中的 Selectors
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这些选择器在某些浏览器中尚处于开发中，功能对应的标准文档可能被修改，在未来的版本中可能发生变化，谨慎使用。
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### :any-link
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匹配有链接锚点的元素，而不管元素是否被访问过。
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即会匹配每一个有 `href`属性的`<a>`，`<area>`，`<link>`的元素，匹配到所有的`:link`或`:visited`。
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``` html
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...
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<style>
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a:any-link {
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border: 1px solid blue;
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color: orange;
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}
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</style>
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...
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<a href="https://example.com">External link</a><br>
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<a href="#">Internal target link</a><br>
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<a>Placeholder link (won't get styled)</a>
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...
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```
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::: caniuse css-any-link
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:::
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### :dir(dir)
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如果元素的内容的书写方向是 dir , 则匹配该元素
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*dir* : ltr | rtl
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``` html
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...
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<style>
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:dir(ltr) {
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background-color: yellow;
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}
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:dir(rtl) {
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background-color: powderblue;
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}
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</style>
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...
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<div dir="rtl">
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<span>test1</span>
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<div dir="ltr">test2
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<div dir="auto">עִבְרִית</div>
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</div>
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</div>
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...
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```
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::: caniuse css-dir-pseudo
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:::
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### :has(selector)
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如果一个元素A恰好满足包含了selector 匹配的元素，则匹配元素A
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``` html
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...
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<style>
|
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a:has(> img) {
|
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background-color: yellow;
|
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}
|
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</style>
|
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...
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<a><img src="example.jpg"></a> <!-- match -->
|
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<a></a>
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...
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```
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::: caniuse css-has
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:::
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||
|
||
### :is() / :any()
|
||
匹配一组选择器选中的元素。
|
||
|
||
优先级是由它的选择器列表中优先级最高的选择器决定。
|
||
|
||
``` html
|
||
...
|
||
<style>
|
||
:is(header, main, footer) p:hover {
|
||
color: red;
|
||
cursor: pointer;
|
||
}
|
||
</style>
|
||
...
|
||
<!-- 等价于 -->
|
||
<style>
|
||
header p:hover,
|
||
main p:hover,
|
||
footer p:hover {
|
||
color: red;
|
||
cursor: pointer;
|
||
}
|
||
</style>
|
||
...
|
||
```
|
||
::: caniuse css-matches-pseudo
|
||
:::
|
||
|
||
### :where()
|
||
匹配一组选择器选中的元素。
|
||
|
||
:where() 的优先级总是为 0。
|
||
``` html
|
||
...
|
||
<style>
|
||
:where(header, main, footer) p:hover {
|
||
color: red;
|
||
cursor: pointer;
|
||
}
|
||
</style>
|
||
...
|
||
<!-- 等价于, 但优先级不同 -->
|
||
<style>
|
||
header p:hover,
|
||
main p:hover,
|
||
footer p:hover {
|
||
color: red;
|
||
cursor: pointer;
|
||
}
|
||
</style>
|
||
...
|
||
```
|