Why doesn't css selector - 'begins with' allow double-dash at end?

问题

In writing CSS I use BEM methodology and I've found using the CSS selector 'begins with' - [class^="classname"] very useful. This is especially true when declaring styles for modifiers, i.e. .block__element--modifier.

Therefore when writing CSS rules I would like to use [class^="block__element--"] to target specific elements regardless of their modifier. However, I've noticed the double-dash at the end of the selector fails to target the elements. A single dash however will work.

I've had a look through the CSS Selectors Level 3 spec but cannot see any mention of why the double-dash would fail.

回答1:

I don't think that should cause you any problem as I just tested with the markup below and it works well...

<div class="block__element--modifier">Hello</div>

div[class^="block__element--"] {
    color: red;
}

Demo

Also, this ^= means that the class name begins with the above string, failing that will result in failure of your selector as well, you may like to use *= instead which searches for a substring.

So if you have a class declared before say like

<div class="hello block__element--modifier">Hello</div>

Will fail your selector Demo, so in this case you may like using

div[class*="block__element--"] {
    color: red;
}

Demo 2

来源：https://stackoverflow.com/questions/22473412/why-doesnt-css-selector-begins-with-allow-double-dash-at-end