String Enum Typed Reducer

string-enum-typed-reducer.ts

// counter.reducer.ts
import { CounterActions, CounterTypes } from './counter.actions';

export function reducer(state: number = 0, action: CounterActions): State {
  switch(action.type) {
    case CounterTypes.INCREMENT: {
      return state + 1;
    }
    case CounterTypes.DECREMENT: {
      return state - 1;
    }
    case CounterTypes.RESET: {
      return action.payload; // typed to number
    }
    default: {
      return state;
    }
  }
}