What types of css selectors are there?

CSS (Cascading Style Sheets) is a style sheet language used for web design. It can make the format of web pages more beautiful and standardized. Selector is a very important concept in CSS, which can be used to select elements in web pages. This article will introduce the classification of CSS selectors to help readers better learn and master CSS.

1. Element selector

The element selector is the most basic selector, which can select HTML elements in web pages. The syntax for an element selector is the name of an HTML element. For example, we can select all paragraph elements with the following CSS code:

p {
  color: red;
}

This code will set the text color of all paragraph elements to red.

2. Class selector

The class selector refers to classifying elements in a web page that have the same attributes but different values, selecting the same class name for them, and then targeting This class name is the selector for styling. The syntactic form of a class selector is a period (.) followed by the class name. For example, we can select elements with the class name "example" through the following CSS code:

.example {
  color: blue;
}

This code will set the text color of all elements with the class name "example" to blue.

3. ID selector

The ID selector is used to identify unique elements in the web page, and each element can only have one ID. The syntax for an ID selector is the pound sign (#) followed by the ID name. For example, we can select the element with the ID "header" through the following CSS code:

#header {
  font-size: 20px;
}

This code will set the font size of the element with the ID "header" to 20px.

4. Descendant selector

The descendant selector can select descendant elements in the web page. The syntax for a descendant selector is to separate the parent and child elements with spaces. For example, we can select p elements in all div elements through the following CSS code:

div p {
  text-align: center;
}

This code will center the text of p elements under all div elements.

5. Adjacent sibling selector

The adjacent sibling selector can select two adjacent sibling elements that meet the conditions. The syntax form of the adjacent sibling selector is to add a plus sign ( ) and the selected element after the qualified element. For example, we can select the ul element adjacent to the div element through the following CSS code:

div + ul {
  list-style: none;
}

This code will remove the list style of the ul element adjacent to the div element.

6. Sub-element selector

The sub-element selector can select sub-elements that meet the conditions. The syntax form of a child element selector is to add a greater than sign (>) and the selected child element after the qualified element. For example, we can select the h1 element, a child element of the div element, through the following CSS code:

div > h1 {
  font-weight: bold;
}

This code will make the font of the h1 element, a child element of the div element, bold.

To sum up, CSS selectors include element selectors, class selectors, ID selectors, descendant selectors, adjacent sibling selectors and child element selectors. Using these selectors correctly can make CSS styles more detailed and flexible. Learning and mastering the use of these selectors will help improve the efficiency and quality of CSS effects.

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