What does :: mean in css

The :: pseudo-class selector in CSS is used to specify the special state or behavior of an element, and is more specific than the pseudo-class selector : and can select specific attributes or states of the element.

:: Meaning in CSS

In CSS, :: is A pseudo-class selector used to specify a special state or behavior of an element. It is similar to the pseudo-class selector :, but it is more specific in that it can select against a specific attribute or state of the element.

Usage

:: The pseudo-class selector can be used to select the following:

• elements A specific state: For example, :hover The pseudo-class selector is used to select elements in the hover state.
• The relationship between elements and other elements: For example, ::first-child The pseudo-class selector is used to select the first child element of the parent element.
• Intrinsic properties of elements: For example, ::before and ::after pseudo-element selectors are used to insert content before or after the element .

Syntax

:: The syntax of the pseudo-class selector is as follows:

<code>element::pseudo-class {
    /* CSS 规则 */
}</code>

Among them, element is the element to target, pseudo-class is the pseudo-class selector to be applied.

Examples

Here are some examples of using the :: pseudo-class selector:

• Select the p element in hover state:

  <code>p:hover {
    color: red;
  }</code>

• Select the first child element of the parent element:

  <code>div::first-child {
    background-color: blue;
  }</code>

• Insert text before element:

  <code>h1::before {
    content: "Hello ";
  }</code>

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