


How to implement a dark mode toggle with JavaScript and CSS variables?
Jul 20, 2025 am 03:52 AMTo achieve dark mode switching, first use CSS variables to define the color scheme, then add a toggle button in HTML, then use JavaScript to switch classes and save user preferences, and finally consider accessibility and transition effects. 1. Define the light and dark mode colors in :root and .dark-mode and apply them to the style; 2. Add the button with id as darkModeToggle; 3. Use JavaScript to listen to click events to switch classes, and save the status through localStorage; 4. Ensure contrast, add transition animations, and support system preferences.
Sure, here's how you can implement a dark mode toggle using JavaScript and CSS variables.

1. Define your color scheme with CSS variables
The first step is to define the colors for both light and dark modes using CSS variables. This makes it easier to switch between them later.
You'll typically set these in the :root
selector for light mode, and then create another class or selector (like .dark-mode
) for dark mode values.

:root { --bg-color: #ffffff; --text-color: #000000; } .dark-mode { --bg-color: #121212; --text-color: #ffffff; }
Then apply those variables in your styles:
body { background-color: var(--bg-color); color: var(--text-color); transition: background-color 0.3s, color 0.3s; }
This sets up the basic visual structure that will change when dark mode is toggled.

2. Add a toggle button in HTML
Next, add a simple button in your HTML where users can click to switch between modes.
<button id="darkModeToggle">Toggle Dark Mode</button>
You can style this button if you want — just make sure it's visible and usable in both themes.
3. Use JavaScript to toggle the dark mode class
Now, write a small piece of JavaScript that toggles the .dark-mode
class on the <body>
element when the button is clicked.
Here's how you can do it:
document.getElementById('darkModeToggle').addEventListener('click', function () { document.body.classList.toggle('dark-mode'); });
This code listens for a click on the button and adds or removes the dark-mode
class from the body depending on its current state.
If you also want to remember the user's preference across sessions, you can store the setting in localStorage
.
// On page load, check localStorage if (localStorage.getItem('darkMode') === 'enabled') { document.body.classList.add('dark-mode'); } // When the user clicks the toggle document.getElementById('darkModeToggle').addEventListener('click', function () { document.body.classList.toggle('dark-mode'); // Save preference if (document.body.classList.contains('dark-mode')) { localStorage.setItem('darkMode', 'enabled'); } else { localStorage.setItem('darkMode', 'disabled'); } });
This way, the user won't have to re-enable dark mode every time they visit your site.
4. Consider accessibility and transitions
Dark mode isn't just about flipping colors. There are a few extra things to keep in mind:
- Contrast : Make sure text remains readable in both modes.
- Transitions : Smooth transitions help avoid jarring visual shifts.
- System preference support : You can default to the user's system preference using media queries.
For example, you can detect if the user prefers dark mode by default:
const prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
And use that as the initial value instead of always starting with light mode.
Also, adding a short transition to the body helps with the theme switch feeling smoother:
body { transition: background-color 0.3s ease, color 0.3s ease; }
That's basically it. It's not too complex, but there are a few little details like saving preferences and handling transitions that make the experience feel more poisoned.
The above is the detailed content of How to implement a dark mode toggle with JavaScript and CSS variables?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

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)

There are three common ways to initiate HTTP requests in Node.js: use built-in modules, axios, and node-fetch. 1. Use the built-in http/https module without dependencies, which is suitable for basic scenarios, but requires manual processing of data stitching and error monitoring, such as using https.get() to obtain data or send POST requests through .write(); 2.axios is a third-party library based on Promise. It has concise syntax and powerful functions, supports async/await, automatic JSON conversion, interceptor, etc. It is recommended to simplify asynchronous request operations; 3.node-fetch provides a style similar to browser fetch, based on Promise and simple syntax

JavaScript data types are divided into primitive types and reference types. Primitive types include string, number, boolean, null, undefined, and symbol. The values are immutable and copies are copied when assigning values, so they do not affect each other; reference types such as objects, arrays and functions store memory addresses, and variables pointing to the same object will affect each other. Typeof and instanceof can be used to determine types, but pay attention to the historical issues of typeofnull. Understanding these two types of differences can help write more stable and reliable code.

Which JavaScript framework is the best choice? The answer is to choose the most suitable one according to your needs. 1.React is flexible and free, suitable for medium and large projects that require high customization and team architecture capabilities; 2. Angular provides complete solutions, suitable for enterprise-level applications and long-term maintenance; 3. Vue is easy to use, suitable for small and medium-sized projects or rapid development. In addition, whether there is an existing technology stack, team size, project life cycle and whether SSR is needed are also important factors in choosing a framework. In short, there is no absolutely the best framework, the best choice is the one that suits your needs.

Hello, JavaScript developers! Welcome to this week's JavaScript news! This week we will focus on: Oracle's trademark dispute with Deno, new JavaScript time objects are supported by browsers, Google Chrome updates, and some powerful developer tools. Let's get started! Oracle's trademark dispute with Deno Oracle's attempt to register a "JavaScript" trademark has caused controversy. Ryan Dahl, the creator of Node.js and Deno, has filed a petition to cancel the trademark, and he believes that JavaScript is an open standard and should not be used by Oracle

CacheAPI is a tool provided by the browser to cache network requests, which is often used in conjunction with ServiceWorker to improve website performance and offline experience. 1. It allows developers to manually store resources such as scripts, style sheets, pictures, etc.; 2. It can match cache responses according to requests; 3. It supports deleting specific caches or clearing the entire cache; 4. It can implement cache priority or network priority strategies through ServiceWorker listening to fetch events; 5. It is often used for offline support, speed up repeated access speed, preloading key resources and background update content; 6. When using it, you need to pay attention to cache version control, storage restrictions and the difference from HTTP caching mechanism.

Promise is the core mechanism for handling asynchronous operations in JavaScript. Understanding chain calls, error handling and combiners is the key to mastering their applications. 1. The chain call returns a new Promise through .then() to realize asynchronous process concatenation. Each .then() receives the previous result and can return a value or a Promise; 2. Error handling should use .catch() to catch exceptions to avoid silent failures, and can return the default value in catch to continue the process; 3. Combinators such as Promise.all() (successfully successful only after all success), Promise.race() (the first completion is returned) and Promise.allSettled() (waiting for all completions)

JavaScript array built-in methods such as .map(), .filter() and .reduce() can simplify data processing; 1) .map() is used to convert elements one to one to generate new arrays; 2) .filter() is used to filter elements by condition; 3) .reduce() is used to aggregate data as a single value; misuse should be avoided when used, resulting in side effects or performance problems.

JavaScript's event loop manages asynchronous operations by coordinating call stacks, WebAPIs, and task queues. 1. The call stack executes synchronous code, and when encountering asynchronous tasks, it is handed over to WebAPI for processing; 2. After the WebAPI completes the task in the background, it puts the callback into the corresponding queue (macro task or micro task); 3. The event loop checks whether the call stack is empty. If it is empty, the callback is taken out from the queue and pushed into the call stack for execution; 4. Micro tasks (such as Promise.then) take precedence over macro tasks (such as setTimeout); 5. Understanding the event loop helps to avoid blocking the main thread and optimize the code execution order.
