What are the hierarchical selectors in html5?

html5 hierarchical selectors include descendant selectors, child element selectors, adjacent sibling selectors, and universal sibling selectors. Detailed introduction: 1. The descendant selector is used to select the descendant elements of an element. It uses spaces to indicate the relationship between elements. 2. The child element selector is used to select the direct child elements of an element. It uses the greater than sign to indicate it. The relationship between elements; 3. 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; 4. The universal sibling selector is used to select the next adjacent sibling element of an element. etc.

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

In HTML5, Hierarchy Selectors are a selector used to select HTML elements with a specific hierarchical relationship. Hierarchical selectors can select specific elements based on relationships between elements. The following are common hierarchical selectors in HTML5:

1. 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 */
   }

In the above example, the descendant selector selects all p elements within the div element.

2. 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 */
   }

In the above example, the child element selector selects the p element that is a direct child element of the div element.

3. 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 */
   }

In the above example, the adjacent sibling selector selects the p element immediately after the h1 element.

4. 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 */
   }

In the above example, the universal sibling selector selects all p elements after the h1 element.

These hierarchical selectors can select specific elements based on the relationship between elements, achieving more precise element selection and style control. By rationally using hierarchical selectors, the readability and maintainability of the code can be improved, while also providing developers with richer style control and layout capabilities.

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

In summary, common hierarchical selectors in HTML5 include descendant selectors, child element selectors, adjacent sibling selectors and universal sibling selectors. Reasonable use of hierarchical selectors can improve the readability and maintainability of code, and also provide developers with richer style control and layout capabilities. If you have any further questions please feel free to let me know.

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