Function reducer

test/typescript/reducers.ts:19–35

(state = 0, action)

  type State = number

  const reducer: Reducer<State> = (state = 0, action) => {
    if (action.type === class="st">'INCREMENT') {
      const { count = 1 } = action
      if (typeof count === class="st">'number') {
        return state + count
      }
    }

    if (action.type === class="st">'DECREMENT') {
      const { count = 1 } = action
      if (typeof count === class="st">'number') {
        return state + count
      }
    }

    return state
  }

  class="cm">// Reducer function accepts any object with `type` prop as action.
  class="cm">// Any extra props are allowed too.