React.useReducer

Refs

• Should I useState or useReducer?

• How to implement useState with useReducer

• Trey’s blog post

type Dispatch<A> = (value: A) => void
type Reducer<S, A> = (prevState: S, action: A) => S
type ReducerState<R extends Reducer<any, any>> = R extends Reducer<infer S, any>
  ? S
  : never
type ReducerAction<R extends Reducer<any, any>> = R extends Reducer<
  any,
  infer A
>
  ? A
  : never
 
function useReducer<R extends Reducer<any, any>, I>(
  reducer: R,
  initializerArg: I & ReducerState<R>,
  initializer: (arg: I & ReducerState<R>) => ReducerState<R>,
): [ReducerState<R>, Dispatch<ReducerAction<R>>]
 
function useReducer<R extends Reducer<any, any>, I>(
  reducer: R,
  initializerArg: I,
  initializer: (arg: I) => ReducerState<R>,
): [ReducerState<R>, Dispatch<ReducerAction<R>>]
 
function useReducer<R extends Reducer<any, any>>(
  reducer: R,
  initialState: ReducerState<R>,
  initializer?: undefined,
): [ReducerState<R>, Dispatch<ReducerAction<R>>]