伪元素伪类

伪元素

伪元素是一个附加至选择器末的关键词，允许对被选择元素的特定部分修改样式

注意

一个选择器中只能使用一个伪元素，伪元素必须跟在普通选择器和基础选择器之后；使用双冒号（::）以便区分伪元素（::）伪类（:）

列举

::after
::before
::backdrop
::first-line
::first-letter
::cue
::grammar-error
::marker
::placeholder --- input::placeholder
::selection
::slotted()
::spelling-error

伪类

伪类是添加到选择器的关键词，指定要选择的元素的特殊状态

列举

伪类	伪类
:active	:last-child
:any-link	:last-of-type
:blank	:left
:checked	:link
:current	:local-link
:default	:not()
:defined	:nth-child()
:dir()	:nth-col()
:disabled	:nth-last-child()
:drop	:nth-last-col()
:empty	:nth-last-of-type()
:enabled	:nth-of-type()
:first	:only-child
:first-child	:only-of-type
:first-of-type	:optional
:fullscreen	:out-of-range
:future	:past
:focus	:placeholder-shown
:focus-visible	:read-only
:focus-within	:read-write
:has()	:required
:host	:right
:host()	:root
:host-context()	:scope
:hover	:target
:indeterminate	:target-within
:in-range	:user-invalid
:invalid	:valid
:is()	:visited
:lang()	:where()