CSS 伪元素是添加到选择器的关键字,可让您设置所选元素的特定部分的样式。例如,样式化元素的第一个字母或行,
在元素内容之前或之后插入内容。所有这些都可以使用 CSS 中的伪元素来完成。
请注意,与伪元素相比,伪类可用于根据元素的状态设置元素的样式。
句法:
selector::pseudo-element {
property: value;
}
CSS 中有很多伪元素,但最常用的如下:
- ::first-line 伪元素将样式应用于块级元素的第一行。请注意,第一行的长度取决于许多因素,包括元素的宽度、文档的宽度和文本的字体大小。请注意,只有少数属性应用于第一行伪元素,如字体属性、颜色属性、背景属性、字间距、字母间距、文本装饰、垂直对齐、文本变换、行高、清除, 等等。
例子:
HTML
first-line Demo
Geeks For Geeks
::first-line element
This is a paragraph using first-line pseudo-element
to style first line of the paragarph.Content in the
first line turns red and becomes bold.
HTML
first-letter Demo
Geeks For Geeks
::first-letter element
This is a paragraph using first-letter pseudo-element
to style first letter of the paragarph.first-letter element
turned the first letter of this paragrapht to red
and made it bold.
HTML
before Demo
Geeks For Geeks
::before element
This is a paragraph to which we added red color quotation marks
using ::before element.
HTML
after Demo
Geeks For Geeks
::after element
This is a paragraph to which we added red color quotation marks
using ::after element.
HTML
marker Demo
Geeks For Geeks
::marker element
- HTML
- CSS
- JavaScript
HTML
selection Demo
Geeks For Geeks
::selection element
Content in this paragraph turns red with
green background on selection.
As this is not a paragraph, you can notice red
background and green text on selection.
输出:
- ::first-letter 伪元素将样式应用于块级元素第一行的第一个字母,但仅限于前面没有其他内容(例如图像或内联表格)的情况。请注意,只有少数属性应用于第一行伪元素,如字体属性、颜色属性、背景属性、字间距、字母间距、文本装饰、垂直对齐、文本变换、行高、清除, 等等。
例子:
HTML
first-letter Demo
Geeks For Geeks
::first-letter element
This is a paragraph using first-letter pseudo-element
to style first letter of the paragarph.first-letter element
turned the first letter of this paragrapht to red
and made it bold.
输出:
- :: before Pseudo-element创建一个伪元素,它是被选元素的第一个子元素。它通常用于向具有 content 属性的元素添加装饰性内容。默认情况下它是内联的。
例子:
HTML
before Demo
Geeks For Geeks
::before element
This is a paragraph to which we added red color quotation marks
using ::before element.
输出:
- ::after Pseudo-element创建一个伪元素,它是所选元素的最后一个子元素。它通常用于向具有 content 属性的元素添加装饰性内容。默认情况下它是内联的。
例子:
HTML
after Demo
Geeks For Geeks
::after element
This is a paragraph to which we added red color quotation marks
using ::after element.
输出:
- ::marker 伪元素选择列表项的标记框,通常包含项目符号或数字。它适用于任何设置为显示的元素或伪元素:列表项,例如
- 和
元素。
例子:
HTML
marker Demo
Geeks For Geeks
::marker element
- HTML
- CSS
- JavaScript
输出:
- ::selection 伪元素将样式应用于文档中已被用户突出显示的部分,例如在文本上单击和拖动鼠标。
例子:
HTML
selection Demo
Geeks For Geeks
::selection element
Content in this paragraph turns red with
green background on selection.
As this is not a paragraph, you can notice red
background and green text on selection.
输出: