What is the use of nth-child?

How to use nth-child: 1. To select an even number of elements, you can use nth-child(even); 2. To select an odd number of elements, you can use nth-child(odd); 3. Select a specific position For elements, you can use specific position indexes; 4. To select a certain range of elements, you can use: nth-child(-n 3) {font-weight: bold;}.

nth-child is a pseudo-class selector in CSS, used to select child elements at specific positions in the parent element. In this article, we will introduce the use of nth-child and some common application scenarios.

1. Basic syntax

nth-child's syntax is as follows:

父元素:nth-child(n)

Among them, the parent element represents the parent element to be selected, and n represents The position of the child element to select.

Note: Positions are counted from 1.

2. Usage Examples

Below we will introduce the usage of nth-child through some specific examples.

1. Select an even number of elements

If you want to select all even-numbered child elements under the parent element, you can use nth-child(even).

For example, to select all even-numbered rows in a list, you can use the following code:

li:nth-child(even) {
background-color: #ccc;
}

2. Select odd-numbered elements

If you want to select all rows under the parent element For child elements at odd positions, nth-child(odd) can be used.

For example, to select all odd-numbered rows in a table, you can use the following code:

tr:nth-child(odd) {
background-color: #ccc;
}

3. Select elements at a specific position

If you only want to select the parent element Child elements at specific positions can use specific position indexes.

For example:

To select the first element in the list, you can use:

li:nth-child(1) {
color: red;
}

To select the last element in the list, you can use:

li:nth-child(n):last-child {
color: blue;
}

4. Select a certain range of elements

nth-child can also select a certain range of elements through formulas.

For example:

To select the first three child elements under a parent element, you can use:

nth-child(-n+3) {
font-weight: bold;
}

To select the last five child elements under a parent element, you can use ：

nth-child(n+6):nth-child(-n+10) {
font-style: italic;
}

3. Notes

When using nth-child, there are several things to pay attention to:

1. The parent element must are elements of the same type. nth-child can only select child elements of the same type. For example, the first div and first span under a parent element cannot be selected.

2. The order of pseudo-class selectors is important. If the nth-child selector is used multiple times in the same style sheet, subsequent rules will overwrite previous rules.

3. nth-child starts counting from 1, not from 0. This is different from how counting is done in some programming languages, please note the difference.

4. Summary

nth-child is a powerful CSS selector. By using different position parameters, you can select child elements at specific positions in the parent element. Whether it is selecting elements at a specific position or selecting elements within a certain range, nth-child can help us achieve it quickly.

However, you need to remember that the use of nth-child must comply with certain rules, especially the parent element must be an element of the same type. I hope this article will help you understand and use nth-child correctly. .

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