What is the usage of hierarchical selector?

What is the usage of hierarchical selector? Specific code examples are needed

The hierarchical selector is a selector in CSS that can pass the relationship between elements. to select specific elements. Hierarchical selectors include child selectors, descendant selectors, adjacent sibling selectors, and general sibling selectors.

The child selector is represented by the greater than sign (>), which indicates the direct child element of the selected element. For example, select all direct child elements with class child under an element with class parent:

.parent > .child {
    //样式
}

The descendant selector is represented by a space to indicate the descendant elements of the selected element. For example, select all descendant elements of class descendant under an element with class ancestor:

.ancestor .descendant {
    //样式
}

The adjacent sibling selector (adjacent sibling selector) is represented by a plus sign ( ) to indicate the selection of adjacent siblings of the element. element. For example, select an element with class element1 followed by a sibling element with class element2:

.element1 + .element2 {
    //样式
}

The general sibling selector is represented by a tilde (~), indicating the general selection of elements. Bro elements. For example, select all following sibling elements of class element2 after an element with class element1:

.element1 ~ .element2 {
    //样式
}

Using a hierarchical selector can select target elements based on the relationship between elements, thereby achieving more precise style control. The following is a specific code example:

HTML code:

<div class="parent">
    <div class="child">这是子元素1</div>
    <div class="child">这是子元素2</div>
</div>
<div class="ancestor">
    <div class="descendant">这是后代元素1</div>
    <div class="descendant">这是后代元素2</div>
</div>
<div class="element1">这是元素1</div>
<div class="element2">这是元素2</div>
<div class="element2">这是元素3</div>

CSS code:

.parent > .child {
    color: red;
}

.ancestor .descendant {
    font-size: 20px;
}

.element1 + .element2 {
    background-color: blue;
}

.element1 ~ .element2 {
    text-align: center;
}

In the above code, through the child selector (.parent > .child ) selects the direct child element in the element with class parent and sets its font color to red. Use the descendant selector (.ancestor .descendant) to select all descendant elements of class descendant under the element of class ancestor and set their font size to 20px. Use the adjacent sibling selector (.element1.element2) to select the sibling element of class element2 immediately following the element with class element1, and set its background color to blue. Use the general sibling selector (.element1 ~ .element2) to select all subsequent sibling elements of class element2 that follow the element with class element1, and display their text in the center.

The use of hierarchical selectors can select HTML elements more flexibly. By combining different hierarchical selectors, we can achieve various style effects. Mastering the use of hierarchical selectors can make CSS styles more maintainable and readable, and can also improve development efficiency.

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