Setup, react dev tools, logging

.vscode/launch.json

@@ -8,7 +8,7 @@
             "type": "chrome",
             "request": "launch",
             "name": "Launch Chrome",
-            "url": "http://localhost:8080",
+            "url": "http://127.0.0.1:3000",
             "webRoot": "${workspaceFolder}"
         },
         {

chapter08/.directory

@@ -0,0 +1,8 @@
+[Dolphin]
+Timestamp=2018,7,29,12,22,28
+Version=4
+ViewMode=1
+VisibleRoles=Details_text,Details_size,Details_modificationtime,Details_destination,Details_permissions,Details_owner,Details_group,CustomizedDetails
+
+[Settings]
+HiddenFilesShown=true

chapter09/.directory

@@ -0,0 +1,8 @@
+[Dolphin]
+Timestamp=2018,7,29,12,22,28
+Version=4
+ViewMode=1
+VisibleRoles=Details_text,Details_size,Details_modificationtime,Details_destination,Details_permissions,Details_owner,Details_group,CustomizedDetails
+
+[Settings]
+HiddenFilesShown=true

chapter09/.eslintrc

@@ -0,0 +1,25 @@
+{
+    "parser": "babel-eslint",
+    "parserOptions": {
+        "ecmaVersion": 2017,
+        "sourceType": "module"
+    },
+    "env": {
+        "node": true,
+        "browser": true,
+        "es6": true,
+        "jest": true
+    },
+    "extends": [
+        "eslint:recommended",
+        "plugin:flowtype/recommended",
+        "plugin:react/recommended"
+    ],
+    "plugins": ["babel", "flowtype", "react"],
+    "rules": {
+        "no-console": "off",
+        "no-var": "error",
+        "prefer-const": "error",
+        "flowtype/no-types-missing-file-annotation": 0
+    }
+}

chapter09/.flowconfig

@@ -0,0 +1,17 @@
+[ignore]
+.*/node_modules/.*
+
+[include]
+
+[libs]
+
+[lints]
+all=warn
+untyped-type-import=off
+unsafe-getters-setters=off
+
+[options]
+include_warnings=true
+module.file_ext=.scss
+
+[strict]

chapter09/.gitignore

@@ -0,0 +1,21 @@
+# See https://help.github.com/ignore-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+
+# testing
+/coverage
+
+# production
+/build
+
+# misc
+.DS_Store
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*

chapter09/.prettierrc

@@ -0,0 +1,5 @@
+{
+    "tabWidth": 4,
+    "printWidth": 75
+}
+

chapter09/config-overrides.js

@@ -0,0 +1,12 @@
+const rewireEslint = require("react-app-rewire-eslint");
+
+function overrideEslintOptions(options) {
+    // do stuff with the eslint options...
+    return options;
+}
+
+/* global module */
+module.exports = function override(config, env) {
+    config = rewireEslint(config, env, overrideEslintOptions);
+    return config;
+};

chapter09/package.json

@@ -0,0 +1,44 @@
+{
+    "name": "chapter09",
+    "version": "0.1.0",
+    "private": true,
+    "devDependencies": {
+        "babel-core": "^6.26.3",
+        "babel-eslint": "^8.2.5",
+        "babel-runtime": "^6.26.0",
+        "eslint": "^5.0.1",
+        "eslint-config-recommended": "^3.0.0",
+        "eslint-plugin-babel": "^5.1.0",
+        "eslint-plugin-flowtype": "^2.49.3",
+        "eslint-plugin-react": "^7.10.0",
+        "flow": "^0.2.3",
+        "flow-bin": "^0.75.0",
+        "flow-coverage-report": "^0.5.0",
+        "flow-typed": "^2.4.0",
+        "react-app-rewire-eslint": "^0.2.3",
+        "react-app-rewired": "^1.5.2",
+        "react-devtools": "^3.2.3",
+        "react-scripts": "1.1.4"
+    },
+    "dependencies": {
+        "axios": "^0.18.0",
+        "connected-react-router": "^4.3.0",
+        "react": "^16.4.1",
+        "react-dom": "^16.4.1",
+        "react-loadable": "^5.4.0",
+        "react-redux": "^5.0.7",
+        "react-router-dom": "^4.3.1",
+        "redux": "^4.0.0",
+        "redux-logger": "^3.0.6",
+        "redux-thunk": "^2.3.0"
+    },
+    "scripts": {
+        "start": "react-app-rewired start",
+        "build": "react-app-rewired build",
+        "test": "react-app-rewired test --env=jsdom",
+        "eject": "react-app-rewired eject",
+        "flow": "flow",
+        "addTypes": "flow-typed install",
+        "devtools": "react-devtools"
+    }
+}

chapter09/public/index.html

@@ -0,0 +1,44 @@
+<!DOCTYPE html>
+<html lang="en">
+
+<head>
+  <!--   <script src="http://192.168.1.200:8097"></script> -->
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
+  <meta name="theme-color" content="#000000">
+  <!--
+      manifest.json provides metadata used when your web app is added to the
+      homescreen on Android. See https://developers.google.com/web/fundamentals/engage-and-retain/web-app-manifest/
+    -->
+  <link rel="manifest" href="%PUBLIC_URL%/manifest.json">
+  <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
+  <!--
+      Notice the use of %PUBLIC_URL% in the tags above.
+      It will be replaced with the URL of the `public` folder during the build.
+      Only files inside the `public` folder can be referenced from the HTML.
+
+      Unlike "/favicon.ico" or "favicon.ico", "%PUBLIC_URL%/favicon.ico" will
+      work correctly both with client-side routing and a non-root public URL.
+      Learn how to configure a non-root public URL by running `npm run build`.
+    -->
+  <title>React App</title>
+</head>
+
+<body>
+  <noscript>
+    You need to enable JavaScript to run this app.
+  </noscript>
+  <div id="root"></div>
+  <!--
+      This HTML file is a template.
+      If you open it directly in the browser, you will see an empty page.
+
+      You can add webfonts, meta tags, or analytics to this file.
+      The build step will place the bundled scripts into the <body> tag.
+
+      To begin the development, run `npm start` or `yarn start`.
+      To create a production bundle, use `npm run build` or `yarn build`.
+    -->
+</body>
+
+</html>

chapter09/public/manifest.json

@@ -0,0 +1,15 @@
+{
+  "short_name": "React App",
+  "name": "Create React App Sample",
+  "icons": [
+    {
+      "src": "favicon.ico",
+      "sizes": "64x64 32x32 24x24 16x16",
+      "type": "image/x-icon"
+    }
+  ],
+  "start_url": "./index.html",
+  "display": "standalone",
+  "theme_color": "#000000",
+  "background_color": "#ffffff"
+}

chapter09/src/App.counter.js

@@ -0,0 +1,23 @@
+/* @flow */
+
+import React, { Component, Fragment } from "react";
+import { Provider } from "react-redux";
+
+import { store } from "./counterApp/store";
+import { ConnectedCounter, ConnectedClicksDisplay } from "./counterApp";
+
+class App extends Component<{}> {
+    render() {
+        return (
+            <Provider store={store}>
+                <Fragment>
+                    <ConnectedCounter />
+                    <hr />
+                    <ConnectedClicksDisplay />
+                </Fragment>
+            </Provider>
+        );
+    }
+}
+
+export default App;

chapter09/src/App.regions.js

@@ -0,0 +1,26 @@
+/* @flow */
+
+import React, { Component, Fragment } from "react";
+import { Provider } from "react-redux";
+
+import {
+    ConnectedCountrySelect,
+    ConnectedRegionsTable
+} from "./regionsApp";
+
+import { store } from "./regionsApp/store";
+
+class App extends Component<{}> {
+    render() {
+        return (
+            <Provider store={store}>
+                <Fragment>
+                    <ConnectedCountrySelect />
+                    <ConnectedRegionsTable />
+                </Fragment>
+            </Provider>
+        );
+    }
+}
+
+export default App;

chapter09/src/counterApp/clicksDisplay.component.js

@@ -0,0 +1,16 @@
+/* @flow */
+
+import React from "react";
+import { PropTypes } from "prop-types";
+
+export class ClicksDisplay extends React.PureComponent<{
+    clicks: number
+}> {
+    static propTypes = {
+        clicks: PropTypes.number.isRequired
+    };
+
+    render() {
+        return <div>Clicks so far: {this.props.clicks}</div>;
+    }
+}

chapter09/src/counterApp/clicksDisplay.connected.js

@@ -0,0 +1,11 @@
+/* @flow */
+
+import { connect } from "react-redux";
+
+import { ClicksDisplay } from "./clicksDisplay.component";
+
+const getProps = state => ({
+    clicks: state.clicks
+});
+
+export const ConnectedClicksDisplay = connect(getProps)(ClicksDisplay);

chapter09/src/counterApp/counter.actions.js

@@ -0,0 +1,29 @@
+/* @flow */
+
+export const COUNTER_INCREMENT = "counter:increment";
+
+export const COUNTER_RESET = "counter:reset";
+
+export type CounterAction = {
+    type: string,
+    value?: number
+};
+
+export const reset = () =>
+    ({
+        type: COUNTER_RESET
+    }: CounterAction);
+
+export const increment = (inc: number) =>
+    ({
+        type: COUNTER_INCREMENT,
+        value: inc
+    }: CounterAction);
+
+export const decrement = (dec: number) =>
+    ({
+        type: COUNTER_INCREMENT,
+        value: -dec
+    }: CounterAction);
+
+// returning increment(-dec) would have worked as well

chapter09/src/counterApp/counter.component.js

@@ -0,0 +1,37 @@
+/* @flow */
+
+import React from "react";
+import { PropTypes } from "prop-types";
+
+import {
+    increment,
+    decrement,
+    reset,
+    CounterAction
+} from "./counter.actions";
+
+export class Counter extends React.PureComponent<{
+    count: number,
+    dispatch: CounterAction => any
+}> {
+    static propTypes = {
+        count: PropTypes.number.isRequired,
+        dispatch: PropTypes.func.isRequired
+    };
+
+    onAdd1 = () => this.props.dispatch(increment(1));
+    onSub2 = () => this.props.dispatch(decrement(2));
+    onReset = () => this.props.dispatch(reset());
+
+    render() {
+        return (
+            <div>
+                Value: {this.props.count}
+                <br />
+                <button onClick={this.onAdd1}>Add 1</button>
+                <button onClick={this.onSub2}>Subtract 2</button>
+                <button onClick={this.onReset}>Reset</button>
+            </div>
+        );
+    }
+}

chapter09/src/counterApp/counter.connected.js

@@ -0,0 +1,9 @@
+/* @flow */
+
+import { connect } from "react-redux";
+
+import { Counter } from "./counter.component";
+
+const getProps = state => ({ count: state.count });
+
+export const ConnectedCounter = connect(getProps)(Counter);

chapter09/src/counterApp/counter.reducer.js

@@ -0,0 +1,28 @@
+/* @flow */
+
+import { COUNTER_INCREMENT, COUNTER_RESET } from "./counter.actions";
+
+import type { CounterAction } from "./counter.actions.js";
+
+export const reducer = (
+    state = {
+        // initial state
+        count: 0,
+        clicks: 0
+    },
+    action: CounterAction
+) => {
+    switch (action.type) {
+        case COUNTER_INCREMENT:
+            return {
+                count: state.count + action.value,
+                clicks: state.clicks + 1
+            };
+
+        case COUNTER_RESET:
+            return { count: 0, clicks: state.clicks + 1 };
+
+        default:
+            return state;
+    }
+};

chapter09/src/counterApp/index.js

@@ -0,0 +1,14 @@
+/* @flow */
+
+import { Counter } from "./counter.component.js";
+import { ConnectedCounter } from "./counter.connected.js";
+
+import { ClicksDisplay } from "./clicksDisplay.component.js";
+import { ConnectedClicksDisplay } from "./clicksDisplay.connected.js";
+
+export {
+    Counter,
+    ConnectedCounter,
+    ClicksDisplay,
+    ConnectedClicksDisplay
+};

chapter09/src/counterApp/store.js

@@ -0,0 +1,10 @@
+/* @flow */
+
+import { createStore, applyMiddleware } from "redux";
+import { createLogger } from "redux-logger";
+
+import { reducer } from "./counter.reducer.js";
+
+const logger = createLogger({ diff: true, duration: true });
+
+export const store = createStore(reducer, applyMiddleware(logger));

chapter09/src/general.css

@@ -0,0 +1,5 @@
+.bordered {
+    border: 1px solid blue;
+    padding: 2px;
+    margin: 4px;
+}

chapter09/src/index.js

@@ -0,0 +1,8 @@
+import React from "react";
+import ReactDOM from "react-dom";
+
+import App from "./App.regions";
+import registerServiceWorker from "./registerServiceWorker";
+
+ReactDOM.render(<App />, document.getElementById("root"));
+registerServiceWorker();

chapter09/src/regionsApp/countrySelect.component.js

@@ -0,0 +1,53 @@
+/* @flow */
+
+import React from "react";
+import PropTypes from "prop-types";
+
+import "../general.css";
+
+export class CountrySelect extends React.PureComponent<{
+    dispatch: ({}) => any
+}> {
+    static propTypes = {
+        loading: PropTypes.bool.isRequired,
+        list: PropTypes.arrayOf(PropTypes.object).isRequired,
+        onSelect: PropTypes.func.isRequired,
+        getCountries: PropTypes.func.isRequired
+    };
+
+    componentDidMount() {
+        if (this.props.list.length === 0) {
+            this.props.getCountries();
+        }
+    }
+
+    onSelect = (e: { target: HTMLOptionElement }) =>
+        this.props.onSelect(e.target.value);
+
+    render() {
+        if (this.props.loading) {
+            return <div className="bordered">Loading countries...</div>;
+        } else {
+            const sortedCountries = [...this.props.list].sort(
+                (a, b) => (a.countryName < b.countryName ? -1 : 1)
+            );
+
+            return (
+                <div className="bordered">
+                    Country:&nbsp;
+                    <select onChange={this.onSelect}>
+                        <option value="">Select a country:</option>
+                        {sortedCountries.map(x => (
+                            <option
+                                key={x.countryCode}
+                                value={x.countryCode}
+                            >
+                                {x.countryName}
+                            </option>
+                        ))}
+                    </select>
+                </div>
+            );
+        }
+    }
+}

chapter09/src/regionsApp/countrySelect.connected.js

@@ -0,0 +1,21 @@
+/* @flow */
+
+import { connect } from "react-redux";
+
+import { CountrySelect } from "./countrySelect.component";
+import { getCountries, getRegions } from "./world.actions";
+
+const getProps = state => ({
+    list: state.countries,
+    loading: state.loadingCountries
+});
+
+const getDispatch = dispatch => ({
+    getCountries: () => dispatch(getCountries()),
+    onSelect: c => dispatch(getRegions(c))
+});
+
+export const ConnectedCountrySelect = connect(
+    getProps,
+    getDispatch
+)(CountrySelect);

chapter09/src/regionsApp/index.js

@@ -0,0 +1,6 @@
+/* @flow */
+
+import { ConnectedCountrySelect } from "./countrySelect.connected.js";
+import { ConnectedRegionsTable } from "./regionsTable.connected.js";
+
+export { ConnectedCountrySelect, ConnectedRegionsTable };

chapter09/src/regionsApp/regionsTable.component.js

@@ -0,0 +1,41 @@
+/* @flow */
+
+import React from "react";
+import PropTypes from "prop-types";
+
+import "../general.css";
+
+export class RegionsTable extends React.PureComponent<{
+    list: Array<{
+        regionCode: string,
+        regionName: string
+    }>
+}> {
+    static propTypes = {
+        list: PropTypes.arrayOf(PropTypes.object).isRequired
+    };
+
+    static defaultProps = {
+        list: []
+    };
+
+    render() {
+        if (this.props.list.length === 0) {
+            return <div className="bordered">No regions.</div>;
+        } else {
+            const ordered = [...this.props.list].sort(
+                (a, b) => (a.regionName < b.regionName ? -1 : 1)
+            );
+
+            return (
+                <div className="bordered">
+                    {ordered.map(x => (
+                        <div key={x.countryCode + "-" + x.regionCode}>
+                            {x.regionName}
+                        </div>
+                    ))}
+                </div>
+            );
+        }
+    }
+}

chapter09/src/regionsApp/regionsTable.connected.js

@@ -0,0 +1,12 @@
+/* @flow */
+
+import { connect } from "react-redux";
+
+import { RegionsTable } from "./regionsTable.component";
+
+const getProps = state => ({
+    list: state.regions,
+    loading: state.loadingRegions
+});
+
+export const ConnectedRegionsTable = connect(getProps)(RegionsTable);

chapter09/src/regionsApp/serviceApi.js

@@ -0,0 +1,9 @@
+/* @flow */
+
+import axios from "axios";
+
+export const getCountriesAPI = () =>
+    axios.get(`http://fk-server:8080/countries`);
+
+export const getRegionsAPI = country =>
+    axios.get(`http://fk-server:8080/regions/${country}`);

chapter09/src/regionsApp/store.js

@@ -0,0 +1,11 @@
+/* @flow */
+
+import { createStore, applyMiddleware } from "redux";
+import thunk from "redux-thunk";
+import { createLogger } from "redux-logger";
+
+import { reducer } from "./worlds.reducer.js";
+
+const logger = createLogger({ duration: true });
+
+export const store = createStore(reducer, applyMiddleware(thunk, logger));

chapter09/src/regionsApp/world.actions.js

@@ -0,0 +1,108 @@
+/* @flow */
+
+import { getCountriesAPI, getRegionsAPI } from "./serviceApi";
+
+// Countries actions
+
+export const COUNTRIES_REQUEST = "countries:request";
+export const COUNTRIES_SUCCESS = "countries:success";
+export const COUNTRIES_FAILURE = "countries:failure";
+
+export type CountriesAction = {
+    type: string,
+    country?: string,
+    listOfCountries?: [object]
+};
+
+export const countriesRequest = () =>
+    ({
+        type: COUNTRIES_REQUEST
+    }: CountriesActions);
+
+export const countriesSuccess = (listOfCountries: []) =>
+    ({
+        type: COUNTRIES_SUCCESS,
+        listOfCountries
+    }: CountriesActions);
+
+export const countriesFailure = () =>
+    ({
+        type: COUNTRIES_FAILURE
+    }: CountriesActions);
+
+// Regions actions
+
+export const REGIONS_REQUEST = "regions:request";
+export const REGIONS_SUCCESS = "regions:success";
+export const REGIONS_FAILURE = "regions:failure";
+
+export type RegionsAction = {
+    type: string,
+    listOfRegions?: [object]
+};
+
+export const regionsRequest = (country: string) =>
+    ({
+        type: REGIONS_REQUEST,
+        country
+    }: RegionsActions);
+
+export const regionsSuccess = (listOfRegions: [{}]) =>
+    ({
+        type: REGIONS_SUCCESS,
+        listOfRegions
+    }: RegionsActions);
+
+export const regionsFailure = () =>
+    ({
+        type: REGIONS_FAILURE
+    }: RegionsActions);
+
+// Complex Actions:
+
+export const getCountries = () => async dispatch => {
+    try {
+        dispatch(countriesRequest());
+        // the next line delays execution for 5 seconds:
+        // await new Promise(resolve => setTimeout(resolve, 5000));
+        const result = await getCountriesAPI();
+        dispatch(countriesSuccess(result.data));
+    } catch (e) {
+        dispatch(countriesFailure());
+    }
+};
+
+export const getRegions = (country: string) => async dispatch => {
+    if (country) {
+        try {
+            dispatch(regionsRequest(country));
+            const result = await getRegionsAPI(country);
+            dispatch(regionsSuccess(result.data));
+        } catch (e) {
+            dispatch(regionsFailure());
+        }
+    } else {
+        dispatch(regionsFailure());
+    }
+};
+
+export const getRegions2 = (country: string) => async (
+    dispatch,
+    getState
+) => {
+    if (country === getState().currentCountry) {
+        console.log("Hey! You are getting the same country as before!");
+    }
+
+    if (country) {
+        try {
+            dispatch(regionsRequest(country));
+            const result = await getRegionsAPI(country);
+            dispatch(regionsSuccess(result.data));
+        } catch (e) {
+            dispatch(regionsFailure());
+        }
+    } else {
+        dispatch(regionsFailure());
+    }
+};

chapter09/src/regionsApp/worlds.reducer.js

@@ -0,0 +1,74 @@
+/* @flow */
+
+import {
+    COUNTRIES_REQUEST,
+    COUNTRIES_SUCCESS,
+    COUNTRIES_FAILURE,
+    REGIONS_REQUEST,
+    REGIONS_SUCCESS,
+    REGIONS_FAILURE
+} from "./world.actions";
+
+import type { CountriesAction, RegionsAction } from "./world.actions";
+
+// import type { CounterAction } from "./world.actions.js";
+
+export const reducer = (
+    state: object = {
+        // initial state
+        loadingCountries: false,
+        currentCountry: "",
+        countries: [],
+        loadingRegions: false,
+        regions: []
+    },
+    action: CountriesAction | RegionsAction
+) => {
+    switch (action.type) {
+        case COUNTRIES_REQUEST:
+            return {
+                ...state,
+                loadingCountries: true,
+                countries: []
+            };
+
+        case COUNTRIES_SUCCESS:
+            return {
+                ...state,
+                loadingCountries: false,
+                countries: action.listOfCountries
+            };
+
+        case COUNTRIES_FAILURE:
+            return {
+                ...state,
+                loadingCountries: false,
+                countries: []
+            };
+
+        case REGIONS_REQUEST:
+            return {
+                ...state,
+                loadingRegions: true,
+                currentCountry: action.country,
+                regions: []
+            };
+
+        case REGIONS_SUCCESS:
+            return {
+                ...state,
+                loadingRegions: false,
+                regions: action.listOfRegions
+            };
+
+        case REGIONS_FAILURE:
+            return {
+                ...state,
+                loadingRegions: false,
+                regions: []
+            };
+
+        default:
+            return state;
+    }
+};

chapter09/src/registerServiceWorker.js

@@ -0,0 +1,117 @@
+// In production, we register a service worker to serve assets from local cache.
+
+// This lets the app load faster on subsequent visits in production, and gives
+// it offline capabilities. However, it also means that developers (and users)
+// will only see deployed updates on the "N+1" visit to a page, since previously
+// cached resources are updated in the background.
+
+// To learn more about the benefits of this model, read https://goo.gl/KwvDNy.
+// This link also includes instructions on opting out of this behavior.
+
+const isLocalhost = Boolean(
+  window.location.hostname === 'localhost' ||
+    // [::1] is the IPv6 localhost address.
+    window.location.hostname === '[::1]' ||
+    // 127.0.0.1/8 is considered localhost for IPv4.
+    window.location.hostname.match(
+      /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
+    )
+);
+
+export default function register() {
+  if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
+    // The URL constructor is available in all browsers that support SW.
+    const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
+    if (publicUrl.origin !== window.location.origin) {
+      // Our service worker won't work if PUBLIC_URL is on a different origin
+      // from what our page is served on. This might happen if a CDN is used to
+      // serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
+      return;
+    }
+
+    window.addEventListener('load', () => {
+      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
+
+      if (isLocalhost) {
+        // This is running on localhost. Lets check if a service worker still exists or not.
+        checkValidServiceWorker(swUrl);
+
+        // Add some additional logging to localhost, pointing developers to the
+        // service worker/PWA documentation.
+        navigator.serviceWorker.ready.then(() => {
+          console.log(
+            'This web app is being served cache-first by a service ' +
+              'worker. To learn more, visit https://goo.gl/SC7cgQ'
+          );
+        });
+      } else {
+        // Is not local host. Just register service worker
+        registerValidSW(swUrl);
+      }
+    });
+  }
+}
+
+function registerValidSW(swUrl) {
+  navigator.serviceWorker
+    .register(swUrl)
+    .then(registration => {
+      registration.onupdatefound = () => {
+        const installingWorker = registration.installing;
+        installingWorker.onstatechange = () => {
+          if (installingWorker.state === 'installed') {
+            if (navigator.serviceWorker.controller) {
+              // At this point, the old content will have been purged and
+              // the fresh content will have been added to the cache.
+              // It's the perfect time to display a "New content is
+              // available; please refresh." message in your web app.
+              console.log('New content is available; please refresh.');
+            } else {
+              // At this point, everything has been precached.
+              // It's the perfect time to display a
+              // "Content is cached for offline use." message.
+              console.log('Content is cached for offline use.');
+            }
+          }
+        };
+      };
+    })
+    .catch(error => {
+      console.error('Error during service worker registration:', error);
+    });
+}
+
+function checkValidServiceWorker(swUrl) {
+  // Check if the service worker can be found. If it can't reload the page.
+  fetch(swUrl)
+    .then(response => {
+      // Ensure service worker exists, and that we really are getting a JS file.
+      if (
+        response.status === 404 ||
+        response.headers.get('content-type').indexOf('javascript') === -1
+      ) {
+        // No service worker found. Probably a different app. Reload the page.
+        navigator.serviceWorker.ready.then(registration => {
+          registration.unregister().then(() => {
+            window.location.reload();
+          });
+        });
+      } else {
+        // Service worker found. Proceed as normal.
+        registerValidSW(swUrl);
+      }
+    })
+    .catch(() => {
+      console.log(
+        'No internet connection found. App is running in offline mode.'
+      );
+    });
+}
+
+export function unregister() {
+  if ('serviceWorker' in navigator) {
+    navigator.serviceWorker.ready.then(registration => {
+      registration.unregister();
+    });
+  }
+}

fixwatcherlimit

@@ -0,0 +1,3 @@
+> sudo sysctl fs.inotify.max_user_watches=200000
+[sudo] password for root:
+fs.inotify.max_user_watches = 200000