react-redux-ts: Reducer

pendingActionsReducer.ts

import ActionTypeKeys, { ActionTypeStates } from "../actions/ActionTypeKeys";
import ActionTypes from "../actions/ActionTypes";
import initialState from "./initialState";

export default function pendingActionsReducer(
  state = initialState.pendingActions,
  action: ActionTypes
) {
  if (actionTypeEndsInInProgress(action.type)) {
    return onInProgressAction(state);
  } else if (
    actionTypeEndsInSuccess(action.type) ||
    actionTypeEndsInFail(action.type)
  ) {
    return onSuccessOrFailAction(state);
  } else {
    return state;
  }
}

function actionTypeEndsInInProgress(type: ActionTypeKeys) {
  const inProgress = ActionTypeStates.INPROGRESS;

  return type.substring(type.length - inProgress.length) === inProgress;
}

function actionTypeEndsInSuccess(type: ActionTypeKeys) {
  const success = ActionTypeStates.SUCCESS;

  return type.substring(type.length - success.length) === success;
}

function actionTypeEndsInFail(type: ActionTypeKeys) {
  const fail = ActionTypeStates.FAIL;

  return type.substring(type.length - fail.length) === fail;
}

function onInProgressAction(state: number) {
  return state + 1;
}

function onSuccessOrFailAction(state: number) {
  return state - 1;
}

rootReducer.ts

import { combineReducers } from "redux";
import IStoreState from "../store/IStoreState";
import isAuthenticated from "./authenticationReducer";
import pendingActions from "./pendingActionsReducer";

const rootReducer = combineReducers<IStoreState>({
  isAuthenticated,
  pendingActions
});

export default rootReducer;