State update is asynchronous in React. So it is possible that there would be old value in count
when you’re updating it next time. Compare, for example, result of these two code samples:
function Counter({initialCount}) {
const [count, setCount] = useState(initialCount);
return (
<>
Count: {count}
<button onClick={() => setCount(initialCount)}>Reset</button>
<button onClick={() => {
setCount(prevCount => prevCount + 1);
setCount(prevCount => prevCount + 1)}
}>+</button>
</>
);
}
and
function Counter({initialCount}) {
const [count, setCount] = useState(initialCount);
return (
<>
Count: {count}
<button onClick={() => setCount(initialCount)}>Reset</button>
<button onClick={() => {
setCount(count + 1);
setCount(count + 1)}
}>+</button>
</>
);
}