What does CSS style cascading mean?
CSS style cascading means that when multiple CSS rules are applied to the same element, the final applied style is determined based on the priority of the rule and the specificity of the rule.
In web development, the cascading nature of styles is very important. Through cascading, developers can easily provide flexibility in website design and layout, and make styles more consistent and easier to maintain. Understanding the principles and usage of style cascading is essential basic knowledge for every front-end developer.
First of all, CSS style cascading determines which style will be applied to the element based on the priority of the rule. The priority is divided into four levels from high to low:
- Inline Style: The style specified directly in the style attribute of the HTML element tag has the highest priority. For example:
<div style="color: red;">Hello World!</div> - ID Selector: Use
The # symbol plus a unique ID specifies the style. For example:#myId { color: blue; } - Class and Attribute Selectors: Use the
.symbol plus the class name or Use the[]symbol plus the attribute name to specify the style. For example:.myClass { color: green; }or[type="text"] { border: 1px solid black; } - Tag selector and pseudo-class Selectors (Tag and Pseudo-class Selectors): Selectors that specify element tag names or specific states, such as
a,div:hover. For example:h1 { font-size: 20px; }ora:hover { text-decoration: underline; }
Secondly, at the same priority Among the rules, specificity affects style cascading. Specificity is a value used to measure the relative weight of style rules. It consists of four parts: the weight of inline styles, the weight of ID selectors, the weights of class selectors and attribute selectors, label selectors and The weight of the pseudo-class selector. Among them, inline styles have the highest weight, followed by ID selectors, class selectors and attribute selectors, and label selectors and pseudo-class selectors have the lowest weights. Rules with higher specificity values have higher priority and will override rules with lower specificity values.
In addition to the above two points, there are some other rules and special cases that will affect the cascading nature of CSS styles:
- !important rules: Using !important rules in styles can The priority of this style rule is raised to the highest level. Use the !important rule with caution, as overuse can make CSS code difficult to maintain.
- Inheritance: Some style attributes are inheritable, that is, child elements will inherit the style of the parent element. When a child element and a parent element have styles with the same attribute, the child element's style will override the parent element's style.
The following is a specific CSS code example to illustrate the use of style cascading:
<!DOCTYPE html>
<html>
<head>
<style>
/* 内联样式 */
p {
color: red !important;
}
/* ID选择器 */
#myId {
color: blue;
}
/* 类选择器和属性选择器 */
.myClass {
color: green;
}
/* 标签选择器和伪类选择器 */
a {
color: purple;
}
</style>
</head>
<body>
<div id="myId" class="myClass">
<p>Hello World!</p>
<a href="#">Visit us</a>
</div>
</body>
</html>In the above example, first we give p The element has an inline style added with the highest priority, sets its color to red, and uses the !important rule. Next, we set an ID selector style for the div element and set its color to blue. Then, we added a class selector style and a label selector style to the div element, with colors green and purple respectively.
Eventually, the color of the p element will have the red color of the inline style applied, while the color of the div element will have the ID selector's blue style applied. Because of specificity rules, class selector styles and label selector styles are ignored. So, the final output is "Hello World!" in red and "Visit us" in blue.
In summary, CSS style cascading determines the final applied style through the priority and specificity of the rules. Understanding the principles of cascading and learning to flexibly use the rules of cascading will help developers better control and manage CSS styles and realize various design needs of the website.
The above is the detailed content of What does CSS style cascading mean?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
How to read excel data in html
Mar 27, 2024 pm 05:11 PM
How to read excel data in html: 1. Use JavaScript library to read Excel data; 2. Use server-side programming language to read Excel data.
Detailed explanation of jQuery reference methods: Quick start guide
Feb 27, 2024 pm 06:45 PM
Detailed explanation of jQuery reference method: Quick start guide jQuery is a popular JavaScript library that is widely used in website development. It simplifies JavaScript programming and provides developers with rich functions and features. This article will introduce jQuery's reference method in detail and provide specific code examples to help readers get started quickly. Introducing jQuery First, we need to introduce the jQuery library into the HTML file. It can be introduced through a CDN link or downloaded
Execute PHP function using onclick
Feb 29, 2024 pm 04:31 PM
We will also cover another way to execute a PHP function through the onclick() event using the Jquery library. This method calls a javascript function, which will output the content of the php function in the web page. We will also demonstrate another way to execute a PHP function using the onclick() event, calling the PHP function using pure JavaScript. This article will introduce a way to execute a PHP function, use the GET method to send the data in the URL, and use the isset() function to check the GET data. This method calls a PHP function if the data is set and the function is executed. Using jQuery to execute a PHP function through the onclick() event we can use
What does hover mean in css
Feb 22, 2024 pm 01:24 PM
:hover in CSS is a pseudo-class selector used to apply specific styles when the user hovers over a specific element. When the mouse hovers over an element, you can add different styles to it through :hover to enhance user experience and interaction. This article will discuss in detail: the meaning of hover and give specific code examples. First, let us understand the basic usage of :hover in CSS. In CSS, you can use a selector to select the element to which the :hover effect is to be applied, and add after it
How to remove the dot in front of the li tag in css
Apr 28, 2024 pm 12:36 PM
There are two ways to remove dots from li tags in CSS: 1. Use the "list-style-type: none;" style; 2. Use transparent images and "list-style-image: url("transparent.png"); "style. Both methods can remove the dots of all li tags. If you only want to remove the dots of certain li tags, you can use a pseudo-class selector.
Use CSS Transform to transform elements
Feb 24, 2024 am 10:09 AM
Usage of Transform in CSS The Transform property of CSS is a very powerful tool that can perform operations such as translation, rotation, scaling and tilting of HTML elements. It can dramatically change the appearance of elements and make web pages more creative and dynamic. In this article, we will introduce the various uses of Transform in detail and provide specific code examples. 1. Translate (Translate) Translate refers to moving an element a specified distance along the x-axis and y-axis. Its syntax is as follows: tran
What is dreamweaver line break?
Apr 08, 2024 pm 09:54 PM
Use the <br> tag in Dreamweaver to create line breaks, which can be inserted through the menu, shortcut keys or direct typing. Can be combined with CSS styles to create empty rows of specific heights. In some cases, it is more appropriate to use the <p> tag instead of the <br> tag because it automatically creates blank lines between paragraphs and applies style control.
What does :: mean in css
Apr 28, 2024 pm 03:45 PM
The :: pseudo-class selector in CSS is used to specify a special state or behavior of an element, and is more specific than the pseudo-class selector : and can select specific attributes or states of an element.
