Ngrx reducer as map

index.ts

const IncrementAction = ...;
const DecrementAction = ...;

const reducer1 = {
  []: () => 0,
  [IncrementAction.type]: (state, action) => state + 1,
  [DecrementAction.type]: (state, action) => state - 1
};

const reducers: { [type: string]: ReduceFn[] } = merge(reducer1, reducer2, ...);

function dispatch(action: Action){
  const newState = reducers[action]?.reduce( (state, reducer) => reducer(state, action), currentState );
}