#selector-pseudo-element-colon-notation

Specify single or double colon notation for applicable pseudo-elements.

指定伪元素使用单冒号还是双冒号。

   a::before { color:pink; }
/** ↑
 * This notation */

The :: notation was chosen for pseudo-elements to establish a discrimination between pseudo-classes (which subclass existing elements) and pseudo-elements (which are elements not represented in the document tree).

伪元素 选择使用 :: 符号是为了区别开 伪类 和 伪元素。

However, for compatibility with existing style sheets, user agents also accept the previous one-colon notation for pseudo-elements introduced in CSS levels 1 and 2 (namely, :first-line, :first-letter, :before and :after).

然而，为了与现有样式表保持兼容，用户代理(user agent)也接受 CSS 1 he 2 中的 伪元素 使用单冒号。

#Options

string: "single"|"double"

#"single"

Applicable pseudo-elements must always use the single colon notation.

伪元素必须使用单冒号。

The following patterns are considered warnings:

以下模式被认为是个警告：

a::before { color: pink; }

a::after { color: pink; }

a::first-letter { color: pink; }

a::first-line { color: pink; }

The following patterns are not considered warnings:

以下模式正常：

a:before { color: pink; }

a:after { color: pink; }

a:first-letter { color: pink; }

a:first-line { color: pink; }

input::placeholder { color: pink; }

li::marker { font-variant-numeric: tabular-nums; }

#"double"

Applicable pseudo-elements must always use the double colon notation.

伪元素必须使用双冒号。

The following patterns are considered warnings:

以下模式被认为是个警告：

a:before { color: pink; }

a:after { color: pink; }

a:first-letter { color: pink; }

a:first-line { color: pink; }

The following patterns are not considered warnings:

以下模式正常：

a::before { color: pink; }

a::after { color: pink; }

a::first-letter { color: pink; }

a::first-line { color: pink; }

input::placeholder { color: pink; }

li::marker { font-variant-numeric: tabular-nums; }