Learn about React Hooks (useState, useEffect) to manage state and side effects in functional components.
Hooks are a feature introduced in React 16.8 that let you use state and other React features without writing a class. They revolutionized how React components are written, enabling a simpler and more powerful functional component paradigm. The two most essential hooks to master are `useState` and `useEffect`. `useState` is the hook for adding state to a functional component. It returns an array with two elements: the current state value and a function that lets you update it. By calling this update function, you tell React to re-render the component with the new state value. This is the foundation of interactivity in modern React. `useEffect` is the hook for handling 'side effects'. A side effect is any operation that affects something outside of the component's render scope, such as fetching data from an API, setting up a subscription, or manually changing the DOM. The function you pass to `useEffect` will run after every render by default. However, you can control when the effect runs by providing a dependency array as a second argument. If the array is empty (`[]`), the effect will run only once, after the initial render, which is perfect for initial data fetching. If the array contains variables, the effect will re-run only when those variables change. `useEffect` can also return a 'cleanup' function, which is used to clean up resources like subscriptions or timers when the component unmounts.