js dynamically modify css
With the continuous development of front-end technology, JavaScript has become an indispensable part of web development. In JavaScript, dynamically modifying CSS styles is one of the common requirements. It can achieve many cool effects, such as special effects when the mouse is hovering, and the navigation bar color changes when the page is scrolled. This article will introduce in detail how to dynamically modify CSS styles in JavaScript.
1. Use JavaScript to modify the style of elements
In HTML, we can beautify the page by adding CSS styles to elements. In JavaScript, the effect of dynamically modifying styles can be achieved by modifying the attributes of elements.
- Using the style attribute of the element
We can use the style attribute of the HTML element to directly modify the style of the element. This method is suitable for modifying the style of a single element.
Sample code:
<div id="box" style="background-color: green;">我是一段文本</div>
In JavaScript, you can dynamically modify its style by getting the style attribute of an element:
var box = document.querySelector('#box'); box.style.backgroundColor = 'red';
After modifying its style through JavaScript, the style of the element will turn red.
- Using the element's style element
Another way to dynamically modify the style of an element is to use the element's style element. The style element allows us to directly access the element's style sheet in JavaScript and modify its style.
Sample code:
<div id="box"></div> <style> #box { background-color: green; } </style>
In JavaScript, you can get the style element by getting the style attribute of the element, and then dynamically modify its style:
var box = document.querySelector('#box'); var styles = box.style; // 修改样式 styles.backgroundColor = 'red';
Modify it through JavaScript After styling, the element's style will turn red.
2. Use classList to modify the style
The two methods introduced above are suitable for modifying the style of a single element. If we need to control the styles of multiple elements on the web page at will, then these two methods This method seems too troublesome. At this point, we can use the classList attribute to dynamically modify the style.
- Add and delete class
The classList attribute contains many convenient methods that allow us to easily add and delete classes. With classes, we can define a set of styles for an element and add or remove them dynamically via JavaScript.
Sample code:
<div class="box">我是一段文本</div>
In JavaScript, you can add or remove classes for elements through the add() and remove() methods of classList:
var box = document.querySelector('.box'); box.classList.add('red'); box.classList.remove('box');
Modify through JavaScript After it is styled, the element's style will turn red, and the element's box class will be deleted.
- Toggle class
In addition to the add() and remove() methods, classList also has a convenient method called toggle(). The toggle() method can switch the class of the element. If the class already exists in the element, the method will delete the class, otherwise it will add the class.
Sample code:
<div class="box">我是一段文本</div>
In JavaScript, you can switch the class of an element through the toggle() method of classList:
var box = document.querySelector('.box'); box.classList.toggle('red'); box.classList.toggle('green');
After modifying its style through JavaScript, the element's class The style will change from red to green.
3. Directly modify the style sheet
The above method can control the style of a single element or multiple elements, but if you need to directly modify the style sheet, you need to use a different method.
In JavaScript, a style sheet is represented as an object, and we can dynamically modify the styles in it through JavaScript code to achieve dynamic modification of the style sheet.
Sample code:
<div class="box">我是一段文本</div>
In JavaScript, you can dynamically modify its style by obtaining the object corresponding to the style sheet:
var styleSheet = document.styleSheets[0]; var rules = styleSheet.cssRules || styleSheet.rules; for (var i = 0; i < rules.length; i++) { var rule = rules[i]; if (rule.selectorText === '.box') { rule.style.backgroundColor = 'red'; } }
After modifying its style through JavaScript, the element's style The style will turn red.
4. Summary
This article introduces three methods of dynamically modifying CSS styles, including using the style attribute of the element, using the style element of the element, and using classList. In addition, in order to meet the need to directly modify the style sheet, we also introduced the method of directly modifying the style sheet. These methods allow us to easily implement the function of dynamically modifying CSS styles in JavaScript.
The above is the detailed content of js dynamically modify css. 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

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

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











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.

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 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

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.

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 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 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

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.
