Learn about the different types of computer compound selectors and their uses

In-depth understanding of the types and usage of computer compound selectors

Introduction: In front-end development, the selection and operation of page elements is very important. In CSS, selectors play a key role. The compound selector is a very powerful selector that can select elements based on multiple conditions. This article will provide an in-depth understanding and analysis of the types and usage of compound selectors.

1. What is a compound selector?

A compound selector is a selector composed of multiple simple selectors. It can accurately select elements on the page based on multiple selection conditions. choose. Compound selectors can improve the flexibility and precision of selectors, allowing us to select the elements that need to be operated more accurately.

2. Basic compound selector type

1. Descendant selector

The descendant selector consists of two or more selectors separated by spaces. , which selects the descendant elements of the specified element. For example, to select the style of all

elements under

elements, you can use the descendant selector ul li.
2. Child element selector

The child element selector consists of two selectors separated by a greater than sign (>). It selects the direct children of the specified element. element. For example, to select styles for all

elements that are direct child elements
• , use the child element selector ul > li.
  3. Adjacent sibling selector

  The adjacent sibling selector consists of two selectors separated by a plus sign ( ). It selects the element immediately following the specified element. The first sibling element after. For example, to select the style of the first adjacent sibling element after all

  elements, you can use the adjacent sibling selector p a.

  4. General sibling selector

  The general sibling selector consists of two selectors separated by a tilde (~). It selects all brothers after the specified element. element. For example, to select the style of all sibling elements after all

  elements, you can use the general sibling selector p ~ a.

  3. Complex compound selector type

  1. Attribute selector

  Attribute selector is used to select elements based on their attribute values. Common attribute selectors have the following forms:

  • [attr]: Select elements with specified attributes.
  • [attr=value]: Select elements with the specified attribute and the attribute value is the specified value.
  • [attr~=value]: Select elements with the specified attribute and the attribute value contains the specified value, separated by spaces.
  • [attr^=value]: Select elements with the specified attribute and the attribute value starting with the specified value.
  • [attr$=value]: Select elements with the specified attribute and the attribute value ends with the specified value.
  • [attr*=value]: Select elements with the specified attribute and the attribute value contains the specified value, without limiting the position.
  2. Pseudo-class selector

  Pseudo-class selector is used to select a specific state or position of an element. Common pseudo-class selectors have the following forms:

  • :hover: Select the state when the mouse is hovering over the element.
  • :active: Select the state when the element is activated.
  • :visited: Select the status of the visited link.
  • :focus: Select the state when focus is obtained.
  • :nth-child(n): Select the nth child element of the element.
  3. Pseudo-element selector

  Pseudo-element selector is used to insert additional content before and after the content of the element. Common pseudo-element selectors have the following forms:

  • ::before: Insert additional content before the content of the element.
  • ::after: Insert additional content after the element's content.
  • ::first-letter: Select the first letter of the element.
  • ::first-line: Select the first line of the element.

  4. Examples of using compound selectors

  The following are some examples of using compound selectors:

  1. Select

     All direct child elements

     within the element:

     div > p

  2. Selects all elements immediately following

     within the

     element The adjacent sibling element after the element:

     p span

  3. Select all

  4. elements in the
     element and contain the attribute class Element with value "active":

     ul li[class=active]

     • Select element's:hover status:

       a :hover

  Summary: The compound selector plays a very important role in CSS. It can select page elements based on multiple conditions. By combining different selectors, we can achieve precise selection and operation of page elements. Mastering the types and usage of compound selectors can improve the work efficiency of front-end developers and make the page present more beautiful visual effects.

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