What are the hierarchical selectors?

Hierarchical selectors include descendant selectors, child element selectors, adjacent sibling selectors, universal sibling selectors, adjacent selectors, etc. Detailed introduction: 1. The descendant selector matches the target element by selecting the descendant elements of the element. It uses spaces to indicate the relationship between elements; 2. The child element selector matches the target element by selecting the direct child elements of the element. It uses The ">" symbol represents the relationship between elements; 3. The adjacent sibling selector matches the target element by selecting the next sibling element of the element. It uses the " " symbol to represent the relationship between elements, etc.

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

The hierarchical selector is a way in CSS to select elements with a specific hierarchical relationship. They match target elements through parent-child, brother, etc. relationships between elements. The following are some common hierarchical selector types:

1. Descendant Selector: Descendant Selector matches the target element by selecting the descendant elements of the element. It uses spaces to indicate relationships between elements. For example, to select all `

` elements inside a `

` element use the descendant selector `div p`.

2. Child Selector: The Child Selector matches the target element by selecting the direct child elements of the element. It uses the `>` symbol to indicate relationships between elements. For example, to select all `

` elements directly inside a `

` element use the child element selector `div > p`.

3. Adjacent Sibling Selector: The adjacent sibling selector matches the target element by selecting the next sibling element of the element. It uses ` ` notation to represent the relationship between elements. For example, to select the `

` element immediately following the `

` element you can use the adjacent sibling selector `h1 p`.

4. General Sibling Selector: The General Sibling Selector matches the target element by selecting all sibling elements of the element. It uses the `~` symbol to indicate the relationship between elements. For example, to select all `

` elements that follow the `

` element you can use the universal sibling selector `h1 ~ p`.

5. Adjacent Selector: The adjacent selector matches the target element by selecting the adjacent elements of the element. It uses ` ` notation to represent the relationship between elements. But unlike the adjacent sibling selector, the adjacent selector requires that the two elements must be on the same level. For example, to select the `

` element immediately following the `

` element you can use the adjacent selector `h1 h2`.

These hierarchical selectors can be combined and nested as needed to select target elements more precisely. For example, you can use a combination of descendant selectors and child selectors to select elements in a specific hierarchical relationship. For example, to select a `

` element that is a direct child of a `

` element, use `div > p`.

When writing CSS styles, flexible use of these hierarchical selectors can help us better control and position elements on the page. However, it should be noted that excessive use of hierarchical selectors may lead to increased complexity of the selector, thereby affecting the performance of the style. Therefore, when choosing an appropriate hierarchical selector, you need to weigh the selector complexity and style requirements for optimal performance and maintainability.

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