伪类 | Pseudo-classes
Pseudo-classes
一个CSS 伪类是一个添加到选择器的关键字，它指定所选元素的特殊状态。例如，当用户悬停在上面时，:hover可以用来改变按钮的颜色。
div:hover {
background-color: #F89B4D;
}
伪类允许您不仅通过与文档树的内容相关，而且还能通过与外部因素如导航器的历史记录（例如:visited），内容的状态（如:checkedon某些表单元素）或鼠标的位置（例如:hover，可让您知道鼠标是否位于元素上方）来将样式应用于元素上。
注意：与伪类相比，pseudo-elements可以用来设置元素的特定部分。
语法
selector:pseudo-class {
property: value;
}
像常规类一样，您可以在选择器中链接尽可能多的伪类。
标准伪类的索引
:active
:any
:checked
:default
:dir()
:disabled
:empty
:enabled
:first
:first-child
:first-of-type
:fullscreen
:focus
:hover
:indeterminate
:in-range
:invalid
:lang()
:last-child
:last-of-type
:left
:link
:not()
:nth-child()
:nth-last-child()
:nth-last-of-type()
:nth-of-type()
:only-child
:only-of-type
:optional
:out-of-range
:read-only
:read-write
:required
:right
:root
:scope
:target
:valid
:visited
规范
| Specification | Status | Comment |
|---|---|---|
| Fullscreen API | Living Standard | Defined :fullscreen. |
| HTML Living Standard | Living Standard | No change from HTML5. |
| Selectors Level 4 | Working Draft | Defined :any-link, :local-link, :scope, :active-drop-target, :valid-drop-target, :invalid-drop-target, :current, :past, :future, :placeholder-shown, :user-error, :blank, :nth-match(), :nth-last-match(), :nth-column(), :nth-last-column(), and :matches(). No significant change for pseudo-classes defined in Selectors Level 3 and HTML5 (though semantic meaning not taken over). |
| HTML5 | Recommendation | Defined the semantic meaning, in the HTML context, of :link, :visited, :active, :enabled, :disabled, :checked, and :indeterminate. Defined :default, :valid, :invalid, :in-range, :out-of-range, :required, :optional, :read-only, :read-write, and :dir(). |
| CSS Basic User Interface Module Level 3 | Candidate Recommendation | Defined :default, :valid, :invalid, :in-range, :out-of-range, :required, :optional, :read-only, and :read-write, but without the associated semantic meaning. |
| Selectors Level 3 | Recommendation | Defined :target, :root, :nth-child(), :nth-last-of-child(), :nth-of-type(), :nth-last-of-type(), :last-child, :first-of-type, :last-of-type, :only-child, :only-of-type, :empty, and :not(). Defined the syntax of :enabled, :disabled, :checked, and :indeterminate, but without the associated semantic meaning. No significant change for pseudo-classes defined in CSS Level 2 (Revision 1). |
| CSS Level 2 (Revision 1) | Recommendation | Defined :lang(), :first-child, :hover, and :focus. No significant change for pseudo-classes defined in CSS Level 1. |
| CSS Level 1 | Recommendation | Defined :link, :visited, and :active, but without the associated semantic meaning. |
