useless_reducer_checker_middlewhere.ts

    // This is usefull for checking unused reducer functions.
    const uselessReducerDetector = storeObj => next => action => {
      let result = next(action);
      let state1 = storeObj.getState();
      let state2 = reducers(state1, result);
      let isEqual = JSON.stringify(state1) === JSON.stringify(state2);
      if (isEqual && action.type[0] !== "@") {
        console.warn(`${action.type} didn't change state. May or may not be useless.`);
      } else {
        return result;
      }
    };