css - 没有媒体类型的@media 规则是做什么的？

Question

我继承了这一点，想知道没有“媒体类型”的媒体查询有什么作用？

 @media (min-width: 768px) {
   .commentlist-item .commentlist-item {
    padding: 0 0 0 2em;
   }
}

根据 www.w3schools.com/css/css3_mediaqueries.asp 的标准语法

  @media not|only mediatype and (expressions) {
    CSS-Code;
}

Answer 1

If the media type is not explicitly given it is all. ~ W3C Media Queries

换句话说，没有媒体类型的@media 规则是简写语法，其中隐含了all。

更多来自规范:

2. Media Queries

A shorthand syntax is offered for media queries that apply to all media types; the keyword all can be left out (along with the trailing and). I.e. if the media type is not explicitly given it is all.

EXAMPLE 5

I.e. these are identical:

@media all and (min-width: 500px) { ... } 
@media (min-width: 500px) { ... }

As are these:

@media (orientation: portrait) { ... }
@media all and (orientation: portrait) { ... }

...

EXAMPLE 7

I.e. these are equivalent:

@media all { ... }
@media { ... }

_{source: https://www.w3.org/TR/css3-mediaqueries/#media0}