What are the html5 compound selectors?

html5 compound selectors have class selectors, ID selectors, attribute selectors, pseudo-class selectors, pseudo-element selectors, descendant selectors, child element selectors, adjacent sibling selectors, and universal Sibling selector and group selector etc. Detailed introduction: 1. The class selector uses the class name to select elements with the same class, which is represented by a dot; 2. The ID selector uses the unique identifier of the element to select a specific element, which is represented by a pound sign; 3. Attribute selectors select elements based on their attribute values, which are represented by square brackets; 4. Pseudo-class selectors, etc.

The operating system for this tutorial: Windows 10 system, HTML5 version, DELL G3 computer.

In HTML5, compound selectors are selectors composed of multiple simple selectors, used to select and position HTML elements more accurately. Compound selectors allow you to combine multiple simple selectors together to satisfy more complex selection criteria. The following are common compound selectors in HTML5:

1. Class Selector:

The class selector uses the class name to select elements with the same class. It is represented by a period (.).

   .class1.class2 {
     /* 选择同时具有class1和class2类的元素 */
   }

2. ID Selector:

The ID selector uses the element's unique identifier (ID) to select a specific element. It is represented by the pound sign (#).

   #myElement {
     /* 选择ID为myElement的元素 */
   }

3. Attribute Selector:

The attribute selector selects elements based on their attribute values. It is represented using square brackets ([]).

   [attribute=value] {
     /* 选择具有指定属性和值的元素 */
   }

4. Pseudo-class Selector:

Pseudo-class selector is used to select a specific state or position of an element. It is represented using a colon (:).

   :hover {
     /* 选择鼠标悬停在元素上的状态 */
   }

5. Pseudo-element Selector:

The pseudo-element selector is used to select a specific part of an element or generated content. It is represented using a double colon (::).

   ::before {
     /* 选择元素的内容前面生成的内容 */
   }

6. Descendant Selector:

The Descendant Selector is used to select the descendant elements of an element. It uses spaces to indicate relationships between elements.

   div p {
     /* 选择div元素内的所有p元素 */
   }

7. Child Selector:

The Child Selector is used to select the direct child elements of an element. It uses the greater than sign (>) to indicate the relationship between elements.

   div > p {
     /* 选择div元素的直接子元素p */
   }

8. Adjacent Sibling Selector:

The Adjacent Sibling Selector is used to select the next adjacent sibling element of an element. It uses the plus sign ( ) to indicate the relationship between elements.

   h1 + p {
     /* 选择紧接在h1元素后的p元素 */
   }

9. General Sibling Selector:

The General Sibling Selector is used to select all sibling elements after an element. It uses the tilde (~) to indicate the relationship between elements.

   h1 ~ p {
     /* 选择h1元素之后的所有p元素 */
   }

10. Group Selector:

The group selector is used to select multiple elements at the same time. It uses commas (,) to separate different selectors.

    h1, h2, h3 {
      /* 选择h1、h2和h3元素 */
    }

Compound selectors can be combined as needed to achieve more precise element selection and style control. By rationally using compound selectors, HTML elements can be better positioned and selected, allowing for more flexible and sophisticated style design.

It should be noted that the use of compound selectors should follow the priority and performance considerations of the selector. Compound selectors that are too complex or nested too deep may cause the selector's matching efficiency to decrease and affect the performance of the page. Therefore, when using compound selectors, you should pay attention to the simplicity and readability of the selector, and make necessary performance optimizations.

The above is the detailed content of What are the html5 compound selectors?. For more information, please follow other related articles on the PHP Chinese website!