CSS Specificity and Inheritance

问题:

Given the following code:

* {
  font-size: 18px;
}

.container {
  font-size: 50%;
}

<div class="container">
  <p>
    Lorem ipsum dolor sit amet, consectetur adipisicing elit. Cupiditate explicabo fugiat laborum minus ullam? Amet delectus facilis id quam temporibus.
  </p>
</div>

The result is that the <p> tag has 18px font-size applied. But shouldn't every element that is inside of the div container inherit the font-size I apply to it? Regardless of the * selector applying the font-size to the <p> tag, because a tag is only worth 1 point and a class is worth 10 points?

回答1:

The .container rule doesn't match the p element. So specificity is irrelevant here. Inheritance and specificity are separate concepts and the only time they interact is when more specific/less specific rules contain declarations with inherit. That is not the case here.

As far as the p element is concerned, only the * rule applies, and the * contains its own font-size declaration, and so the specified font size follows that declaration.

If the * rule didn't have its own font-size declaration, then the p element would inherit from .container.

If you want descendants of .container to take after its font size, you will need an additional .container * rule. Be very careful with the inherit keyword when it comes to relative values, though — you probably meant to keep all descendants the same size, so 1em or 100% is more appropriate here than inherit:

* {
  font-size: 18px;
}

.container {
  font-size: 50%;
}

.container * {
  font-size: 1em;
}

<div class="container">
  <p>
    Lorem ipsum dolor sit amet, consectetur adipisicing elit. Cupiditate explicabo fugiat laborum minus ullam? Amet delectus facilis id quam temporibus.
  </p>
</div>

回答2:

The * takes precedence over the parent selector as you did for container. You should be able to reach your point adding to the p

font-size: inherit;

Or also this should work:

.container * {
    font-size: inherit;
}

回答3:

The star * is the universal selector for CSS. It matches a single element of any type. Please see this link, has a good explanation (why) is the CSS star selector considered harmful?