Why does React state behave like a snapshot, and what does this handler log?

Direct answer

If count is 0 when the click starts, the handler logs 0; setCount schedules a future render where count becomes 1.

Counter.jsx

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

  function handleClick() {
    setCount(count + 1);
    console.log(count);
  }

  return <button onClick={handleClick}>{count}</button>;
}

Output

Each render receives its own state snapshot. Calling the setter queues an update, but it does not rewrite the count variable inside the event handler that is already running.