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::before 和 :after 中双冒号和单冒号有什么区别？ #15

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ScoutYin opened this issue Jan 9, 2019 · 0 comments
Open

::before 和 :after 中双冒号和单冒号有什么区别？ #15

ScoutYin opened this issue Jan 9, 2019 · 0 comments

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@ScoutYin
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ScoutYin commented Jan 9, 2019

类似:link, :hover等，单冒号是用来表示伪类的，伪元素在CSS1中已存在，当时语法是用 : 表示，如 :before 和 :after，但是CSS3做了修订，伪元素用 :: 表示，如 ::before 和 ::after，以此区分伪元素和伪类；由于低版本IE对双冒号不兼容，开发者为了兼容性各浏览器，继续使使用 :after 这种老语法表示伪元素；综上所述：::before 是 CSS3 中写伪元素的新语法； :after 是 CSS1 中存在的、兼容IE的老语法。
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