Learn basic CSS code selectors: start from scratch and become familiar with the classification and application of selectors

Quick Start CSS Code Basic Selector: Learn the classification and application of selectors from scratch

CSS (Cascading Style Sheets) is used to control the style of HTML documents A markup language. In CSS, a selector is used to select the HTML element to which a style should be applied. Simply put, selectors are used to specify which HTML elements will be affected by CSS styles.

There are many types of selectors, and you can choose the appropriate selector according to your needs and application scenarios. This article will introduce the basic classification and application of CSS selectors from scratch to help readers quickly get started with CSS code.

1. Element selector

The element selector is the simplest and most basic selector, which selects the corresponding element through the tag name of the HTML element. For example, to select all paragraph elements, you can use the following selector:

p {
    color: red;
}

p in the above code is an element selector, which selects all <p> tag elements and set their text color to red. </p> <ol start="2"><li>Class selector</li></ol> <p>The class selector selects elements by specifying a name in the <code>class attribute of the HTML element. This selector allows us to select elements with the same class name and apply the same style to them. For example, to select all elements with the class name highlight, you can use the following selector:

.highlight {
    background-color: yellow;
}

.highlight in the above code is a class selector , which selects all elements with the class name highlight and sets their background color to yellow.

3. ID Selector

The ID selector selects elements by specifying a unique name in the id attribute of the HTML element. Unlike class selectors, ID selectors can only select one element because the value of the ID attribute must be unique within an HTML document. For example, to select the element with the ID header, you can use the following selector:

#header {
    font-size: 24px;
}

#header in the above code is an ID selector, which selects Remove the elements with ID header and set their font size to 24 pixels.

4. Descendant selector

The descendant selector selects elements by selecting descendant elements of HTML elements. Descendant elements refer to the child elements, grandson elements, great-grandson elements, etc. of the selected element. For example, to select <p></p> elements under all <div> elements, you can use the following selector: <pre class='brush:php;toolbar:false;'>div p { font-weight: bold; }</pre><p>## in the above code #div p<code> is a descendant selector that selects all

elements under all

elements and sets their font to bold .

Direct child element selector

The direct child element selector selects elements by selecting the direct child elements of an HTML element. Direct child elements refer to the direct child elements of the selected element, not its descendants. For example, to select all <p></p>

elements that are direct children of

, you can use the following selector:

div > p {
    color: blue;
}

# in the above code ##div > p

is a direct child element selector, which selects all direct child elements <p></p> of the <div> element and adds them The text color is set to blue. <code>In addition to the above five basic selectors, there are more types of selectors such as pseudo-class selectors and attribute selectors that can be used to select elements. Understanding and mastering the classification and application of these selectors can help us better control the style of HTML elements.

To sum up, by learning and applying CSS selectors, we can flexibly control and manage the styles of HTML elements and achieve a variety of web page layouts and designs. I hope this article can help readers quickly get started with CSS code and improve their web design and development capabilities.