Building a Dark Mode Toggle in React with Context API

Dark mode is a must-have feature in modern web apps. It enhances user experience and can reduce eye strain. In this post, we'll walk through how to implement a Dark Mode Toggle in a React app using the Context API to manage state globally.

We'll create a simple app where users can toggle between dark and light modes, with their preference stored in localStorage so it persists even after they leave or reload the page.

Step 1: Set up the Context

The first step is to create a ThemeContext that will provide the dark mode state and the toggle function to any component in the app.

// src/context/ThemeContext.js
import React, { createContext, useState, useEffect } from 'react';

export const ThemeContext = createContext();

export const ThemeProvider = ({ children }) => {
  const [darkMode, setDarkMode] = useState(() => {
    const savedMode = localStorage.getItem('dark-mode');
    return savedMode === 'true' || false;
  });

  useEffect(() => {
    localStorage.setItem('dark-mode', darkMode);
    document.body.className = darkMode ? 'dark-mode' : '';
  }, [darkMode]);

  const toggleDarkMode = () => {
    setDarkMode((prevMode) => !prevMode);
  };

  return (
    <ThemeContext.Provider value={{ darkMode, toggleDarkMode }}>
      {children}
    </ThemeContext.Provider>
  );
};

Here, we're using useState to initialize the theme based on localStorage. useEffect ensures that whenever the theme changes, it updates localStorageand applies the appropriate class to the body element.

Step 2: Create the Toggle Component

Here, we use useContext to consume the darkModevalue and toggleDarkMode function from the ThemeContext.

// src/components/ThemeToggle.js
import React, { useContext } from 'react';
import { ThemeContext } from '../context/ThemeContext';

const ThemeToggle = () => {
  const { darkMode, toggleDarkMode } = useContext(ThemeContext);

  return (
    <button onClick={toggleDarkMode}>
      {darkMode ? 'Switch to Light Mode' : 'Switch to Dark Mode'}
    </button>
  );
};

export default ThemeToggle;

Step 3: Apply Dark Mode Styles

To see the dark mode in action, you'll need to add some CSS styles. For simplicity, we'll apply a dark theme to the bodyelement.

/* src/styles.css */
body {
  margin: 0;
  font-family: sans-serif;
  transition: background-color 0.3s ease;
}

body.dark-mode {
  background-color: #121212;
  color: white;
}

Step 4: Set up the App Component

Here, we wrap the entire app inside the ThemeProvider, which allows the dark mode state and toggle function to be available globally.

// src/App.js
import React from 'react';
import { ThemeProvider } from './context/ThemeContext';
import ThemeToggle from './components/ThemeToggle';
import './styles.css';

function App() {
  return (
    <ThemeProvider>
      <div className="App">
        <h1>Dark Mode Toggle with Context API</h1>
        <ThemeToggle />
      </div>
    </ThemeProvider>
  );
}

export default App;

By using React's Context API, we made the dark mode state easily accessible across the app without prop-drilling. Adding localStorage ensures the theme preference persists, even after a page reload or revisit.

Feel free to tweak this basic implementation by adding more components and styles as per your needs.

If you'd like to see more of my work, check out my portfolio vrushikvisavadiya

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Building a Dark Mode Toggle in React with Context API

Vrushik Visavadiya

Step 1: Set up the Context

Step 2: Create the Toggle Component

Step 3: Apply Dark Mode Styles

Step 4: Set up the App Component

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