State with useState

Remembering Values Between Renders

Regular JavaScript variables reset on every render. useState gives a component persistent memory — when you call the setter, React re-renders the component with the new value.

import { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
      <button onClick={() => setCount(c => c - 1)}>Decrement</button>
      <button onClick={() => setCount(0)}>Reset</button>
    </div>
  );
}

Functional updates

When the new state depends on the old state, always use the functional form of the setter: setState(prev => prev + 1). This guarantees you get the most recent value, even when multiple state updates are batched.