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ReactIntermediate#hooks
ReactAdvanced#hooks#state
When should you use useReducer instead of useState?
Use useReducer when several values change together, the next state depends on the previous one through many actions, or you want the update logic testable outside the component.
Example
function reducer(s, a) {
switch (a.type) {
case 'inc': return { ...s, n: s.n + 1 };
default: return s;
}
}
const [state, dispatch] = useReducer(reducer, { n: 0 });
dispatch({ type: 'inc' });