typescriptintermediate

useDarkMode Hook

Dark mode hook that syncs with system preferences and persists user choice to localStorage.

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import { useState, useEffect } from 'react';

export function useDarkMode() {
  const [isDark, setIsDark] = useState(() => {
    if (typeof window === 'undefined') return false;
    const stored = localStorage.getItem('dark-mode');
    if (stored !== null) return stored === 'true';
    return window.matchMedia('(prefers-color-scheme: dark)').matches;
  });

  useEffect(() => {
    const root = document.documentElement;
    if (isDark) {
      root.classList.add('dark');
    } else {
      root.classList.remove('dark');
    }
    localStorage.setItem('dark-mode', String(isDark));
  }, [isDark]);

  useEffect(() => {
    const mq = window.matchMedia('(prefers-color-scheme: dark)');
    const handler = (e: MediaQueryListEvent) => {
      if (localStorage.getItem('dark-mode') === null) {
        setIsDark(e.matches);
      }
    };
    mq.addEventListener('change', handler);
    return () => mq.removeEventListener('change', handler);
  }, []);

  return { isDark, toggle: () => setIsDark(p => !p), setIsDark };
}