CSS属性选择器：引号上的规则（"'，'或none？） [英] CSS attribute selectors: The rules on quotes (", ' or none?)

问题描述

这个问题已经扰乱我一段时间了。当写一个CSS选择器与一个元素的属性比较如此。

  a [rel =nofollow] 
  

我从来不知道我应该用什么引号。他们真的有必要吗？

基本上，这是什么规格，因为我不能在网站上找到它。

这些都被视为有效吗？

  a [rel =nofollow] 
a [rel ='nofollow'] 
a [rel = nofollow] 
  

解决方案

我在此处更详细地介绍了此主题：

只要属性值是字母数字，通常可以省略引号（但是，有一些例外 - 有关所有详细信息，请参阅链接文章）。无论如何，我发现这是一个好的做法，无论如何添加引号，如果你需要它们，即 a [href ^ = http：//] 将无法工作， a [href ^ =http：//] 将。

CSS规范中的章节。

This question has been bugging me for a while now. When writing a CSS selector that compares against an element's attribute like so.

a[rel="nofollow"]

I never know what I should be doing with the quotation marks. Are they really necessary?

Basically, what is the specification for this because I can't find it on the web site.

Are all of these considered valid?

a[rel="nofollow"]
a[rel='nofollow']
a[rel=nofollow]

解决方案

I’ve written more extensively on the subject here: Unquoted attribute values in HTML and CSS.

I’ve also created a tool to help you answer your question: http://mothereff.in/unquoted-attributes

You can usually omit the quotes as long as the attribute value is alphanumeric (however, there are some exceptions — see the linked article for all the details). Anyhow, I find it to be good practice to add the quotes anyway in case you need them, i.e. a[href^=http://] won’t work, but a[href^="http://"] will.

The article I mentioned links to the appropriate chapters in the CSS spec.

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