history.js

// Get initial state from the previously saved data in local storage
let getHistoryFromLocal = () => {
    let value = localStorage.getItem('WeatherHistory')
    return JSON.parse(value) || [];
}

// Maintain a history list of queried weather data of 10
let getUpdatedHistory = (history, value) => {
    let updateList = [...history];
    if (updateList.length >= 10) {
        updateList.shift();
    }
    updateList.push(value);
    return updateList;
}

const history = (state = getHistoryFromLocal(), action) => {
    switch (action.type) {
        case "UPDATE_HISTORY":
            return getUpdatedHistory(state, action.payload);
        default:
            return state;
    }
};

export default history;

index.js

import { combineReducers } from 'redux'
import weather from './weather';
import zipCode from './zipCode';
import temperature from "./temperature";
import history from "./history";

export default combineReducers({
    zipCode,
    weather,
    temperature,
    history
})

temperature.js

// Default temperature to use Fahrenheit (imperial, °F)
const temperature = (state = "imperial", action) => {
    switch (action.type) {
        case "SAVE_TEMPERATURE":
            return action.payload;
        default:
            return state;
    }
};

export default temperature;

weather.js

// Preloads saved weather data from local storage, if available
let getWeatherFromLocal = () => {
    let value = localStorage.getItem('CurrentWeatherData');
    return JSON.parse(value) || "";
}

const weather = (state = getWeatherFromLocal(), action) => {
    switch (action.type) {
        case "SAVE_WEATHER_DATA":
            return action.payload;
        default:
            return state;
    }
};

export default weather;

zipCode.js

// Default zipcode will be 10001
const zipCode = (state = 10001, action) => {
    switch (action.type) {
        case "SAVE_ZIP":
            return action.payload
        default:
            return state;
    }
};

export default zipCode;