CSS Selectors

选择器指示那些元素会被应用上样式。

基本选择器

元素类型选择器

这个基本的选择器选择所有给定的元素名的元素
Syntax: elename
Example: input 将会选择所有的 <input> 元素.

类选择器

这个基本的选择器选择所有含有给定类名的元素
Syntax: .classname
Example: .index 会匹配所有包含 index 类的元素 (类似与有一个类似于这样的属性class="index").

ID选择器

这个基本的选择器会选择所有id属性与之匹配的元素。需要注意的是一个文档中每个id都应该是唯一的。
Syntax: #idname
Example: #toc 将会匹配所有id属性为 toc 的元素 (类似于这样的定义 id="toc").

通用选择器

这个基本选择器选择所有节点。它也常常和一个名词空间配合使用，用来选择该空间下的所有元素。
Syntax: * ns|* *|*
Example: * 将会将会选择所有元素。

属性选择器

这个基本的选择器根据元素的属性来进行选择。
Syntax: [attr] [attr=value] [attr~=value] [attr|=value] [attr^=value] [attr$=value] [attr*=value]
Example: [autoplay] 将会选择所有具有 autoplay 属性的元素（不论这个属性的值是什么）

Combinators

Adjacent sibling selectors

The '+' combinator selects nodes that immediately follow the former specified element.
Syntax: A + B
Example: ul + li will match any <li> that immediately follows a <ul>.

General sibling selectors

The '~' combinator selects nodes that follow (not necessarily immediately) the former specified element, if both elements shared the same parent.
Syntax: A ~ B
Example: p ~ span will match all <span> elements that follow a <p> element inside the same element.

Child selectors

The '>' combinator selects nodes that are direct children of the former specified element.
Syntax: A > B
Example: ul > li will match all <li> elements that are inside a <ul> element.

Descendant selectors

The ' ' combinator selects nodes that are children (not necessary direct children) of the former specified element.
Syntax: A B
Example: div span will match any <span> element that is inside a <div> element.

Pseudo-elements

Pseudo-elements are abstractions of the tree representing entities beyond what HTML does. For example, HTML doesn't have an element describing the first letter or line of a paragraph, or the marker of a list. Pseudo-elements represent these entities and allow CSS rules to be associated with them. that way, these entitities can be styled independently.

Pseudo-classes

Pseudo-classes allow to select elements based on information that is not contained in the document tree like a state or that is particularly complex to extract. E.g. they match if a link has been previously visited or not.

Specifications

Browser compatibility