What is the Context API and when should you use it?

Context API provides a way to share data across components without prop drilling. Use it for global data like themes, user authentication, or language preferences.

// Create context
const ThemeContext = createContext();

// Provider
function App() {
  return (
    <ThemeContext.Provider value="dark">
      <Header />
    </ThemeContext.Provider>
  );
}

// Consumer
function Header() {
  const theme = useContext(ThemeContext);
  return <div className={theme}>Header</div>;
}