什么:: before和:: after是什么意思？ [英] What do ::before and ::after mean?

问题描述

我在看一对Twitter的Bootstrap模板，我看到很多 :: 和 ::之后插入 div 标记之前和之后。

I was looking at a couple Twitter Bootstrap templates and I saw that a lot of ::before and ::after were inserted before and after div tags.

任何人都可以告诉我他们是什么？

Can anybody tell me what they are?

推荐答案

伪元素，你不直接包括在你的标记，但可以使用CSS创建一些整洁的效果。你已经提到了 :: before 和 :: after 之后，它们代表伪元素，

They represent pseudo-elements, which you don't include directly in your markup, but are available to you to create some neat effects with CSS. You have mentioned ::before and ::after, and they represent pseudo-elements that appear, shockingly, before and after your elements.

整个列表包含在下面，应该是非常清楚的：

The whole list is included below and should be fairly self-explanatory:

::after 
::before 
::first-letter 
::first-line 
::selection

ref： https://developer.mozilla.org/en-US/docs/Web/CSS/Pseudo-elements

注意使用双冒号，这与规范一致。有时你会看到用单个冒号指定的伪元素，但这只是因为我们需要支持不理解双冒号语法的浏览器。

Note the use of the double-colon, which is consistent with the spec. Sometimes you will see pseudo-elements specified with a single colon, but that was only because we needed to support browsers that didn't understand the double-colon syntax.

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