Function of create a reduce function for Redux store

createReduce.js

function createReduce(reducer = {}, initialState) {
  return (state = initialState, action) => {
    const { type: actionType } = action;
    const func = reducer[actionType];
    const newState = typeof func === 'function' ? func.call(reducer, state, action) : undefined;
    return newState !== undefined ? newState : state;
  };
}

// example

const SOME_ACTION = 'SOME_ACTION';

const reducer = { [SOME_ACTION]: (state, { payload }) => payload };

const reduce = createReduce(reducer);

const state = false;

const action = { type: SOME_ACTION, payload: true };

const newState = reduce(state, action);
// => newState is true