Dark mode toggle with JavaScript in Tailwind - Mini Project: Build & Apply

Dark mode toggle with JavaScript

📖 Scenario: You want to add a button on your website that lets visitors switch between light and dark themes. This helps people who prefer dark backgrounds to feel comfortable while browsing.

🎯 Goal: Build a simple webpage with a button that toggles dark mode on and off using JavaScript and Tailwind CSS classes.

📋 What You'll Learn

Create a basic HTML structure with a heading and a toggle button

Use Tailwind CSS classes for styling light and dark modes

Add a JavaScript variable to track the dark mode state

Write JavaScript code to toggle the dark mode class on the html element when the button is clicked

💡 Why This Matters

🌍 Real World

Many websites offer dark mode to reduce eye strain and improve user experience in low light. This project shows how to add a simple toggle for that feature.

💼 Career

Front-end developers often implement theme toggles using JavaScript and CSS frameworks like Tailwind. Understanding this helps build accessible and user-friendly interfaces.

1

Create the basic HTML structure

Write the HTML skeleton with lang="en", charset="UTF-8", and a viewport meta tag. Inside the body, add a main section containing an h1 heading with the text Dark Mode Toggle and a button with the text Toggle Dark Mode. Use Tailwind classes p-6 on main, text-3xl font-bold mb-4 on the heading, and px-4 py-2 bg-blue-500 text-white rounded on the button.

Tailwind

  
  
  Dark Mode Toggle
  


  
    Dark Mode Toggle
    Toggle Dark Mode
    
  

Need a hint?

Remember to include the lang attribute in the html tag and use the exact Tailwind classes for spacing and colors.

2

Add a JavaScript variable to track dark mode

Add a <script> tag just before the closing </body> tag. Inside it, create a variable called isDarkMode and set it to false.

Tailwind

  
  
  Dark Mode Toggle
  


  
    Dark Mode Toggle
    Toggle Dark Mode
  
  
    // Create a variable called isDarkMode and set it to false
    // Your code here
  

Need a hint?

Use let isDarkMode = false; inside the <script> tag.

3

Add JavaScript to toggle dark mode class

Inside the existing <script> tag, select the button element using document.querySelector and store it in a variable called toggleButton. Then add a click event listener to toggleButton. Inside the event listener function, toggle the value of isDarkMode (true becomes false, false becomes true). Then use document.documentElement.classList.toggle('dark') to add or remove the dark mode class on the html element.

Tailwind

  
  
  Dark Mode Toggle
  


  
    Dark Mode Toggle
    Toggle Dark Mode
  
  
    let isDarkMode = false;
    // Select the button and add a click event listener to toggle dark mode
    // Your code here
  

Need a hint?

Use document.querySelector('button') to get the button. Then add a click event listener that toggles isDarkMode and the dark class on document.documentElement.

4

Add Tailwind dark mode styles and accessibility

Add the class="dark:bg-gray-900 dark:text-white" to the body tag to style the background and text color in dark mode. Also add aria-pressed="false" to the button for accessibility. Inside the event listener, update the button's aria-pressed attribute to the current isDarkMode value as a string.

Tailwind

  
  
  Dark Mode Toggle
  


  
    Dark Mode Toggle
    Toggle Dark Mode
  
  
    let isDarkMode = false;
    const toggleButton = document.querySelector('button');
    toggleButton.addEventListener('click', () => {
      isDarkMode = !isDarkMode;
      document.documentElement.classList.toggle('dark');
      // Update aria-pressed attribute
      // Your code here
    });
  

Need a hint?

Add the dark mode background and text color classes to the body tag. Add aria-pressed="false" to the button. Update aria-pressed inside the click event using setAttribute.