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Creating Light/Dark Theme Toggles in Your App

Posted on May 19, 2025May 19, 2025 by Sagar Kunwar

Creating Light/Dark Theme Toggles in Your App

Hello there, fellow coder! If you find yourself spending a lot of time working on apps, you’ve probably noticed the ever-popular light/dark theme toggle. Whether you’re someone who loves the crisp brightness of light mode, or you lean towards the cool vibes of dark mode, having the option to switch can make a huge difference in user experience. Today, I’m going to guide you step-by-step on how to implement a light/dark theme toggle in your app. Ready to get started? Let’s dive in!

Why Have a Theme Toggle?

Before diving into the code, let’s discuss why adding a theme toggle can be beneficial:
– User Preference: People have different preferences; offering options can improve satisfaction.
– Readability: Dark themes can reduce eye strain, especially in low-light conditions.
– Aesthetics: It allows users to personalize their experience, which can make your app stand out.

Setting Up Your Environment

We’ll be using HTML, CSS, and JavaScript for this tutorial. To keep things simple, all you need is a text editor and a browser. No fancy tools required!

HTML Structure

First, let’s create a basic HTML structure. This will include a button to toggle the theme and a few lines of sample text.

html





Light/Dark Theme Toggle




Hello, World!







Styling with CSS

Let’s style our app. We’ll define both light and dark themes in CSS.

css
body {
font-family: Arial, sans-serif;
transition: background-color 0.3s, color 0.3s;
}

.container {
text-align: center;
padding: 50px;
}

.light-theme {
background-color: #ffffff;
color: #000000;
}

.dark-theme {
background-color: #121212;
color: #ffffff;
}

button {
padding: 10px 20px;
cursor: pointer;
margin-top: 20px;
}

JavaScript Magic

Now, let’s add the JavaScript to handle the toggle. We’ll allow the button to switch between light and dark themes.

javascript
const toggleButton = document.getElementById('theme-toggle');
const body = document.body;

toggleButton.addEventListener('click', () => {
if (body.classList.contains('light-theme')) {
body.classList.replace('light-theme', 'dark-theme');
} else {
body.classList.replace('dark-theme', 'light-theme');
}
});

Default Theme

It’s always a good idea to set a default theme when the page loads. We can add this to our script.js.

javascript
window.onload = () => {
body.classList.add('light-theme'); // default is light theme
};

Making It Persistent

To make the theme persistent, even after a page reload, let’s use localStorage.

Update your event listener in script.js:

javascript
toggleButton.addEventListener('click', () => {
const isLight = body.classList.contains('light-theme');
body.classList.toggle('light-theme', !isLight);
body.classList.toggle('dark-theme', isLight);
localStorage.setItem('theme', isLight ? 'dark-theme' : 'light-theme');
});

window.onload = () => {
const savedTheme = localStorage.getItem('theme') || 'light-theme';
body.classList.add(savedTheme);
};

Test and Experiment

Open your HTML file in a browser and play around with the toggle. You should be able to switch themes effortlessly, and the selected theme will persist even if you refresh the page.

Possible Enhancements

Here are a few ideas you can try:
– CSS Variables: Make the theme colors scalable using CSS variables for easier management.
– Animation: Add snazzy transition effects for the toggle switch.
– Icon Change: Use SVG icons to switch between a sun and moon icon when toggling themes.

Conclusion

Congratulations! You’ve just built a light/dark theme toggle for your app. Not only is this a great way to improve user experience, but it’s also an excellent exercise in understanding the basics of DOM manipulation and local storage in JavaScript.

Take this further by integrating the theme toggle into an actual project or adding more features. The world is your oyster!

Happy coding, and don’t hesitate to reach out if you hit a snag or want to share your cool creations. Keep building, keep learning!

—

Optional Practice Ideas:

– Implement this in a framework like React or Vue.js.
– Allow users to choose from multiple color schemes beyond just light and dark.
– Combine this with a user setting panel to store additional preferences.

Thanks for joining in on this coding journey! If you have questions or suggestions, feel free to leave a comment below.

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