Demystifying CSS basic selectors: in-depth analysis of how to use various selectors

CSS (Cascading Style Sheets) is a language used to describe the style of web pages. In CSS, selectors are a way to select elements to which styles need to be applied. There are many ways to use selectors, each with its own characteristics and applicable scenarios. This article will provide an in-depth analysis of the usage of various basic CSS selectors to help readers better understand and apply CSS.

1. ID Selector

The ID selector is the most specific and priority selector in CSS. It is prefixed by a "#" symbol, followed by the ID attribute value of the element to be selected. For example, to select an element with the id "header", you can use the following code:

#header {
    color: red;
}

The advantage of the ID selector is that it has a higher priority and can override the style settings of other selectors for the same element. Certainly. However, the disadvantage of the ID selector is that it is unique and the ID can only be used once per web page. Therefore, ID selectors are used in some specific scenarios, such as navigation bars, headers, and other elements that only have one.

2. Class selector

The class selector is one of the most commonly used selectors in CSS. It is prefixed by a "." symbol, followed by the class name of the element to be selected. For example, to select all button elements with the class name "btn", you can use the following code:

.btn {
    background-color: blue;
}

The advantage of the class selector is that it can be reused. An element can have multiple class names at the same time. Selectors can select and apply the same style. Class selectors can also be added for cascade selection by adding other selectors, making them more flexible and powerful.

3. Tag selector

The tag selector is the most basic and common selector in CSS. It uses the HTML element tag name as a selector to select specific HTML elements. For example, to select all paragraph elements, you would use code like this:

p {
    font-size: 16px;
}

The advantage of the tag selector is that it is highly versatile and suitable for selecting multiple elements and applying the same style. Tag selectors can also be combined with other selectors for more precise selection.

4. Attribute selector

Attribute selector is a way to select elements based on their attributes. It surrounds the attribute name with "[]" symbols, and elements can be selected by combining the attribute name and attribute value. For example, to select all elements containing the "data-" attribute, you can use the following code:

[data-*] {
    color: green;
}

The attribute selector has high flexibility and scalability, and can select different attributes based on different attributes and attribute values. element and apply the style.

5. Pseudo-class selector

Pseudo-class selector is a way to select elements based on their special status or specific conditions. For example, to select the link element that is currently active, you can use the following code:

a:active {
    color: orange;
}

The advantage of the pseudo-class selector is that it can select elements in a special state and apply styles. Common pseudo-class selectors include: link (unvisited link), :visited (visited link), :hover (mouse hover state), :focus (obtain focus state), etc.

By in-depth analysis of the usage of the above various basic CSS selectors, we can better understand and apply CSS. Different selectors are suitable for different scenarios and needs. Choosing the correct selector can improve the efficiency and maintainability of CSS code. In practical applications, we can flexibly select appropriate selectors according to specific needs, and achieve more precise selections by combining selectors. At the same time, we must also pay attention to the priority and weight of the selector to avoid style conflicts and overrides. Strengthening the understanding and proficient use of basic CSS selectors can help us better develop and design web pages and provide a better user experience.

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