react_add-eslint.diff

diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..3494874
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,10 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+[*.{js,ts,jsx,tsx,json,md}]
+indent_style = space
+indent_size = 2
+
diff --git a/.eslintrc.js b/.eslintrc.js
new file mode 100644
index 0000000..081d167
--- /dev/null
+++ b/.eslintrc.js
@@ -0,0 +1,26 @@
+module.exports = {
+  env: {
+    browser: true,
+    es6: true,
+    node: true,
+  },
+  extends: [
+    "react-app",
+    "eslint:recommended",
+    "plugin:@typescript-eslint/eslint-recommended",
+    "plugin:@typescript-eslint/recommended",
+  ],
+  globals: {
+    Atomics: "readonly",
+    SharedArrayBuffer: "readonly",
+  },
+  parser: "@typescript-eslint/parser",
+  parserOptions: {
+    ecmaVersion: 11,
+  },
+  ignorePatterns: [],
+  plugins: ["@typescript-eslint", "prettier"],
+  rules: {
+    "prettier/prettier": "error",
+  },
+};
diff --git a/package.json b/package.json
index 6e34eaf..19d18b0 100644
--- a/package.json
+++ b/package.json
@@ -15,14 +15,21 @@
     "react-scripts": "3.4.1",
     "typescript": "^3.7.5"
   },
+  "devDependencies": {
+    "eslint": "^6.6.0",
+    "eslint-plugin-import": "^2.20.2",
+    "eslint-plugin-node": "^11.1.0",
+    "eslint-plugin-prettier": "^3.1.3",
+    "eslint-plugin-promise": "^4.2.1",
+    "prettier": "^2.0.5"
+  },
   "scripts": {
     "start": "react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test",
-    "eject": "react-scripts eject"
-  },
-  "eslintConfig": {
-    "extends": "react-app"
+    "eject": "react-scripts eject",
+    "lint": "npm run lint:exec -- src/**/*.{ts,tsx,js,jsx}",
+    "lint:exec": "eslint"
   },
   "browserslist": {
     "production": [
diff --git a/src/App.test.tsx b/src/App.test.tsx
index 4db7ebc..352d7b8 100644
--- a/src/App.test.tsx
+++ b/src/App.test.tsx
@@ -1,8 +1,8 @@
-import React from 'react';
-import { render } from '@testing-library/react';
-import App from './App';
+import React from "react";
+import { render } from "@testing-library/react";
+import App from "./App";
 
-test('renders learn react link', () => {
+test("renders learn react link", () => {
   const { getByText } = render(<App />);
   const linkElement = getByText(/learn react/i);
   expect(linkElement).toBeInTheDocument();
diff --git a/src/App.tsx b/src/App.tsx
index a53698a..bc328b6 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1,8 +1,8 @@
-import React from 'react';
-import logo from './logo.svg';
-import './App.css';
+import React from "react";
+import logo from "./logo.svg";
+import "./App.css";
 
-function App() {
+function App(): React.ReactElement {
   return (
     <div className="App">
       <header className="App-header">
diff --git a/src/index.tsx b/src/index.tsx
index f5185c1..9710934 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -1,14 +1,14 @@
-import React from 'react';
-import ReactDOM from 'react-dom';
-import './index.css';
-import App from './App';
-import * as serviceWorker from './serviceWorker';
+import React from "react";
+import ReactDOM from "react-dom";
+import "./index.css";
+import App from "./App";
+import * as serviceWorker from "./serviceWorker";
 
 ReactDOM.render(
   <React.StrictMode>
     <App />
   </React.StrictMode>,
-  document.getElementById('root')
+  document.getElementById("root")
 );
 
 // If you want your app to work offline and load faster, you can change
diff --git a/src/serviceWorker.ts b/src/serviceWorker.ts
index b09523f..167f43a 100644
--- a/src/serviceWorker.ts
+++ b/src/serviceWorker.ts
@@ -11,9 +11,9 @@
 // opt-in, read https://bit.ly/CRA-PWA
 
 const isLocalhost = Boolean(
-  window.location.hostname === 'localhost' ||
+  window.location.hostname === "localhost" ||
     // [::1] is the IPv6 localhost address.
-    window.location.hostname === '[::1]' ||
+    window.location.hostname === "[::1]" ||
     // 127.0.0.0/8 are considered localhost for IPv4.
     window.location.hostname.match(
       /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
@@ -25,13 +25,10 @@ type Config = {
   onUpdate?: (registration: ServiceWorkerRegistration) => void;
 };
 
-export function register(config?: Config) {
-  if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
+export function register(config?: Config): void {
+  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.href
-    );
+    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
     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
@@ -39,7 +36,7 @@ export function register(config?: Config) {
       return;
     }
 
-    window.addEventListener('load', () => {
+    window.addEventListener("load", () => {
       const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
 
       if (isLocalhost) {
@@ -50,8 +47,8 @@ export function register(config?: Config) {
         // 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://bit.ly/CRA-PWA'
+            "This web app is being served cache-first by a service " +
+              "worker. To learn more, visit https://bit.ly/CRA-PWA"
           );
         });
       } else {
@@ -62,24 +59,24 @@ export function register(config?: Config) {
   }
 }
 
-function registerValidSW(swUrl: string, config?: Config) {
+function registerValidSW(swUrl: string, config?: Config): void {
   navigator.serviceWorker
     .register(swUrl)
-    .then(registration => {
-      registration.onupdatefound = () => {
+    .then((registration) => {
+      registration.onupdatefound = (): void => {
         const installingWorker = registration.installing;
         if (installingWorker == null) {
           return;
         }
-        installingWorker.onstatechange = () => {
-          if (installingWorker.state === 'installed') {
+        installingWorker.onstatechange = (): void => {
+          if (installingWorker.state === "installed") {
             if (navigator.serviceWorker.controller) {
               // At this point, the updated precached content has been fetched,
               // but the previous service worker will still serve the older
               // content until all client tabs are closed.
               console.log(
-                'New content is available and will be used when all ' +
-                  'tabs for this page are closed. See https://bit.ly/CRA-PWA.'
+                "New content is available and will be used when all " +
+                  "tabs for this page are closed. See https://bit.ly/CRA-PWA."
               );
 
               // Execute callback
@@ -90,7 +87,7 @@ function registerValidSW(swUrl: string, config?: Config) {
               // 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.');
+              console.log("Content is cached for offline use.");
 
               // Execute callback
               if (config && config.onSuccess) {
@@ -101,25 +98,25 @@ function registerValidSW(swUrl: string, config?: Config) {
         };
       };
     })
-    .catch(error => {
-      console.error('Error during service worker registration:', error);
+    .catch((error) => {
+      console.error("Error during service worker registration:", error);
     });
 }
 
-function checkValidServiceWorker(swUrl: string, config?: Config) {
+function checkValidServiceWorker(swUrl: string, config?: Config): void {
   // Check if the service worker can be found. If it can't reload the page.
   fetch(swUrl, {
-    headers: { 'Service-Worker': 'script' }
+    headers: { "Service-Worker": "script" },
   })
-    .then(response => {
+    .then((response) => {
       // Ensure service worker exists, and that we really are getting a JS file.
-      const contentType = response.headers.get('content-type');
+      const contentType = response.headers.get("content-type");
       if (
         response.status === 404 ||
-        (contentType != null && contentType.indexOf('javascript') === -1)
+        (contentType != null && contentType.indexOf("javascript") === -1)
       ) {
         // No service worker found. Probably a different app. Reload the page.
-        navigator.serviceWorker.ready.then(registration => {
+        navigator.serviceWorker.ready.then((registration) => {
           registration.unregister().then(() => {
             window.location.reload();
           });
@@ -131,18 +128,18 @@ function checkValidServiceWorker(swUrl: string, config?: Config) {
     })
     .catch(() => {
       console.log(
-        'No internet connection found. App is running in offline mode.'
+        "No internet connection found. App is running in offline mode."
       );
     });
 }
 
-export function unregister() {
-  if ('serviceWorker' in navigator) {
+export function unregister(): void {
+  if ("serviceWorker" in navigator) {
     navigator.serviceWorker.ready
-      .then(registration => {
+      .then((registration) => {
         registration.unregister();
       })
-      .catch(error => {
+      .catch((error) => {
         console.error(error.message);
       });
   }
diff --git a/src/setupTests.ts b/src/setupTests.ts
index 74b1a27..5fdf001 100644
--- a/src/setupTests.ts
+++ b/src/setupTests.ts
@@ -2,4 +2,4 @@
 // allows you to do things like:
 // expect(element).toHaveTextContent(/react/i)
 // learn more: https://github.com/testing-library/jest-dom
-import '@testing-library/jest-dom/extend-expect';
+import "@testing-library/jest-dom/extend-expect";