puzzle 07 · javascript
After clicking once, what is count?
const [count, setCount] = useState(0);
function onClick() {
setCount(count + 1);
setCount(count + 1);
}2
1
0
It depends on batching
why
Both calls read the same `count` from the render's closure, so both compute 0 + 1. The second overwrites the first. Use the updater form — setCount(c => c + 1) — to queue on the latest value and get 2.