Home Web Front-end Front-end Q&A css dynamic changes

css dynamic changes

May 27, 2023 am 11:06 AM

CSS dynamic change is a common front-end technology, which can change the appearance of the web page by changing the styles in the CSS style sheet, making the web page more lively. This article will introduce the principles, implementation methods and practical applications of CSS dynamic changes.

1. Principle

In HTML, the display of text, pictures, links and other elements are defined by CSS style sheets. A CSS style sheet is a combination of properties and their values ​​that determine the display effect of each element on a web page. CSS style sheets are composed of selectors and declarations. Selectors specify the HTML elements to which styles are applied, and declarations describe how these elements should be rendered.

The principle of CSS dynamic change is actually very simple, which is to change the appearance of the web page by modifying the attribute values ​​of the specified elements in the CSS style sheet through JavaScript. For example, change the background color, font size, position, border style, etc. of an element. Since JavaScript can directly operate the Document Object Model (DOM), it can easily obtain the node information and attribute values ​​​​of each element in the page, and this information is the basic data required to change the CSS style sheet.

2. Implementation methods

Applying CSS dynamic changes in HTML pages usually has the following implementation methods:

1. Use JS attribute operations

This method is relatively simple, just modify the style attribute of the element directly through JS. For example:

document.getElementById("myDiv").style.backgroundColor = "red";

This line of code sets the background color of the HTML element with the ID "myDiv" to red .

2. Use CSS class switching

This method requires defining multiple CSS classes in advance, and then selecting the required class in the JS code to change the element style. This method is clearer, but requires the creation of multiple additional CSS classes. For example:

CSS definition:

.myClass {
background-color: yellow;
}

.myClass2 {
background-color: red ;
}

JS code:

document.getElementById("myDiv").className = "myClass2";

This line of code will set the ID as "myDiv" The class name of the HTML element is switched from "myClass" to "myClass2", thus changing the background color.

3. Use the StyleSheet object

This method requires obtaining the style sheet object, and then changing the element style by operating the rules in the style sheet. This method is more flexible, but the code is relatively complex. For example:

CSS definition:

.myClass {
background-color: yellow;
}

JS code:

var styleSheet = document.styleSheets[0];
var rules = styleSheet.cssRules || styleSheet.rules;
rules[0].style.backgroundColor = "red";

This code is obtained first The first style sheet object, and then get the style rule collection rules. Finally, change the background color of the first rule to red through rules[0].style.backgroundColor.

3. Example application

1. Change the background color of the element

The following code can be used to change the background color of the element to random when the mouse is placed on an element. Color:

document.getElementById('myElement').addEventListener('mouseover', function () {

var r = Math.floor(Math.random() * 256);
var g = Math.floor(Math.random() * 256);
var b = Math.floor(Math.random() * 256);
this.style.backgroundColor = 'rgb(' + r + ',' + g + ',' + b + ')';
Copy after login

});

2.Change text color

The following code can be used to change the color of the text in the specified element to red, green, and blue in turn when the button is clicked:

var colors = ['red', 'green', ' blue'];
var currentIndex = 0;
document.getElementById('myButton').addEventListener('click', function () {
document.getElementById('myText').style.color = colors[currentIndex];
currentIndex ;
if (currentIndex == colors.length) {

  currentIndex = 0;
Copy after login

}
});

3. Change the image size

The following code can be used to double the size of the image when the image is clicked:

document.getElementById('myImage').addEventListener('click', function () {
var width = this.width * 2;
var height = this.height * 2;
this.style.width = width 'px';
this.style.height = height 'px';
});

The above three examples demonstrate the basic application methods of CSS dynamic changes, and more special effects can be achieved by changing different attributes. It should be noted that although CSS dynamic changes can make web pages more lively and interesting, they must be kept moderate and not have a negative impact on the user experience.

The above is the detailed content of css dynamic changes. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Java Tutorial
1664
14
PHP Tutorial
1268
29
C# Tutorial
1242
24
React's Role in HTML: Enhancing User Experience React's Role in HTML: Enhancing User Experience Apr 09, 2025 am 12:11 AM

React combines JSX and HTML to improve user experience. 1) JSX embeds HTML to make development more intuitive. 2) The virtual DOM mechanism optimizes performance and reduces DOM operations. 3) Component-based management UI to improve maintainability. 4) State management and event processing enhance interactivity.

Frontend Development with React: Advantages and Techniques Frontend Development with React: Advantages and Techniques Apr 17, 2025 am 12:25 AM

The advantages of React are its flexibility and efficiency, which are reflected in: 1) Component-based design improves code reusability; 2) Virtual DOM technology optimizes performance, especially when handling large amounts of data updates; 3) The rich ecosystem provides a large number of third-party libraries and tools. By understanding how React works and uses examples, you can master its core concepts and best practices to build an efficient, maintainable user interface.

React and the Frontend: Building Interactive Experiences React and the Frontend: Building Interactive Experiences Apr 11, 2025 am 12:02 AM

React is the preferred tool for building interactive front-end experiences. 1) React simplifies UI development through componentization and virtual DOM. 2) Components are divided into function components and class components. Function components are simpler and class components provide more life cycle methods. 3) The working principle of React relies on virtual DOM and reconciliation algorithm to improve performance. 4) State management uses useState or this.state, and life cycle methods such as componentDidMount are used for specific logic. 5) Basic usage includes creating components and managing state, and advanced usage involves custom hooks and performance optimization. 6) Common errors include improper status updates and performance issues, debugging skills include using ReactDevTools and Excellent

React's Ecosystem: Libraries, Tools, and Best Practices React's Ecosystem: Libraries, Tools, and Best Practices Apr 18, 2025 am 12:23 AM

The React ecosystem includes state management libraries (such as Redux), routing libraries (such as ReactRouter), UI component libraries (such as Material-UI), testing tools (such as Jest), and building tools (such as Webpack). These tools work together to help developers develop and maintain applications efficiently, improve code quality and development efficiency.

The Future of React: Trends and Innovations in Web Development The Future of React: Trends and Innovations in Web Development Apr 19, 2025 am 12:22 AM

React's future will focus on the ultimate in component development, performance optimization and deep integration with other technology stacks. 1) React will further simplify the creation and management of components and promote the ultimate in component development. 2) Performance optimization will become the focus, especially in large applications. 3) React will be deeply integrated with technologies such as GraphQL and TypeScript to improve the development experience.

React vs. Backend Frameworks: A Comparison React vs. Backend Frameworks: A Comparison Apr 13, 2025 am 12:06 AM

React is a front-end framework for building user interfaces; a back-end framework is used to build server-side applications. React provides componentized and efficient UI updates, and the backend framework provides a complete backend service solution. When choosing a technology stack, project requirements, team skills, and scalability should be considered.

React: The Power of a JavaScript Library for Web Development React: The Power of a JavaScript Library for Web Development Apr 18, 2025 am 12:25 AM

React is a JavaScript library developed by Meta for building user interfaces, with its core being component development and virtual DOM technology. 1. Component and state management: React manages state through components (functions or classes) and Hooks (such as useState), improving code reusability and maintenance. 2. Virtual DOM and performance optimization: Through virtual DOM, React efficiently updates the real DOM to improve performance. 3. Life cycle and Hooks: Hooks (such as useEffect) allow function components to manage life cycles and perform side-effect operations. 4. Usage example: From basic HelloWorld components to advanced global state management (useContext and

Understanding React's Primary Function: The Frontend Perspective Understanding React's Primary Function: The Frontend Perspective Apr 18, 2025 am 12:15 AM

React's main functions include componentized thinking, state management and virtual DOM. 1) The idea of ​​componentization allows splitting the UI into reusable parts to improve code readability and maintainability. 2) State management manages dynamic data through state and props, and changes trigger UI updates. 3) Virtual DOM optimization performance, update the UI through the calculation of the minimum operation of DOM replica in memory.

See all articles