Initialize project using Create React App

src/App.css

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+.App {
+  text-align: center;
+}
+
+.App-logo {
+  height: 40vmin;
+  pointer-events: none;
+}
+
+@media (prefers-reduced-motion: no-preference) {
+  .App-logo {
+    animation: App-logo-float infinite 3s ease-in-out;
+  }
+}
+
+.App-header {
+  min-height: 100vh;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  font-size: calc(10px + 2vmin);
+}
+
+.App-link {
+  color: rgb(112, 76, 182);
+}
+
+@keyframes App-logo-float {
+  0% {
+    transform: translateY(0);
+  }
+  50% {
+    transform: translateY(10px)
+  }
+  100% {
+    transform: translateY(0px)
+  }
+}

src/App.js

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+import React from 'react';
+import logo from './logo.svg';
+import { Counter } from './features/counter/Counter';
+import './App.css';
+
+function App() {
+  return (
+    <div className="App">
+      <header className="App-header">
+        <img src={logo} className="App-logo" alt="logo" />
+        <Counter />
+        <p>
+          Edit <code>src/App.js</code> and save to reload.
+        </p>
+        <span>
+          <span>Learn </span>
+          <a
+            className="App-link"
+            href="https://reactjs.org/"
+            target="_blank"
+            rel="noopener noreferrer"
+          >
+            React
+          </a>
+          <span>, </span>
+          <a
+            className="App-link"
+            href="https://redux.js.org/"
+            target="_blank"
+            rel="noopener noreferrer"
+          >
+            Redux
+          </a>
+          <span>, </span>
+          <a
+            className="App-link"
+            href="https://redux-toolkit.js.org/"
+            target="_blank"
+            rel="noopener noreferrer"
+          >
+            Redux Toolkit
+          </a>
+          ,<span> and </span>
+          <a
+            className="App-link"
+            href="https://react-redux.js.org/"
+            target="_blank"
+            rel="noopener noreferrer"
+          >
+            React Redux
+          </a>
+        </span>
+      </header>
+    </div>
+  );
+}
+
+export default App;

src/App.test.js

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+import React from 'react';
+import { render } from '@testing-library/react';
+import { Provider } from 'react-redux';
+import store from './app/store';
+import App from './App';
+
+test('renders learn react link', () => {
+  const { getByText } = render(
+    <Provider store={store}>
+      <App />
+    </Provider>
+  );
+
+  expect(getByText(/learn/i)).toBeInTheDocument();
+});

src/app/store.js

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+import { configureStore } from '@reduxjs/toolkit';
+import counterReducer from '../features/counter/counterSlice';
+
+export default configureStore({
+  reducer: {
+    counter: counterReducer,
+  },
+});

src/features/counter/Counter.js

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+import React, { useState } from 'react';
+import { useSelector, useDispatch } from 'react-redux';
+import {
+  decrement,
+  increment,
+  incrementByAmount,
+  incrementAsync,
+  selectCount,
+} from './counterSlice';
+import styles from './Counter.module.css';
+
+export function Counter() {
+  const count = useSelector(selectCount);
+  const dispatch = useDispatch();
+  const [incrementAmount, setIncrementAmount] = useState('2');
+
+  return (
+    <div>
+      <div className={styles.row}>
+        <button
+          className={styles.button}
+          aria-label="Increment value"
+          onClick={() => dispatch(increment())}
+        >
+          +
+        </button>
+        <span className={styles.value}>{count}</span>
+        <button
+          className={styles.button}
+          aria-label="Decrement value"
+          onClick={() => dispatch(decrement())}
+        >
+          -
+        </button>
+      </div>
+      <div className={styles.row}>
+        <input
+          className={styles.textbox}
+          aria-label="Set increment amount"
+          value={incrementAmount}
+          onChange={e => setIncrementAmount(e.target.value)}
+        />
+        <button
+          className={styles.button}
+          onClick={() =>
+            dispatch(incrementByAmount(Number(incrementAmount) || 0))
+          }
+        >
+          Add Amount
+        </button>
+        <button
+          className={styles.asyncButton}
+          onClick={() => dispatch(incrementAsync(Number(incrementAmount) || 0))}
+        >
+          Add Async
+        </button>
+      </div>
+    </div>
+  );
+}

src/features/counter/Counter.module.css

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+.row {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.row:not(:last-child) {
+  margin-bottom: 16px;
+}
+
+.value {
+  font-size: 78px;
+  padding-left: 16px;
+  padding-right: 16px;
+  margin-top: 2px;
+  font-family: 'Courier New', Courier, monospace;
+}
+
+.button {
+  appearance: none;
+  border: none;
+  background: none;
+  font-size: 32px;
+  padding-left: 12px;
+  padding-right: 12px;
+  outline: none;
+  border: 2px solid transparent;
+  color: rgb(112, 76, 182);
+  padding-bottom: 4px;
+  cursor: pointer;
+  background-color: rgba(112, 76, 182, 0.1);
+  border-radius: 2px;
+  transition: all 0.15s;
+}
+
+.textbox {
+  font-size: 32px;
+  padding: 2px;
+  width: 64px;
+  text-align: center;
+  margin-right: 8px;
+}
+
+.button:hover, .button:focus {
+  border: 2px solid rgba(112, 76, 182, 0.4);
+}
+
+.button:active {
+  background-color: rgba(112, 76, 182, 0.2);
+}
+
+.asyncButton {
+  composes: button;
+  position: relative;
+  margin-left: 8px;
+}
+
+.asyncButton:after {
+  content: "";
+  background-color: rgba(112, 76, 182, 0.15);
+  display: block;
+  position: absolute;
+  width: 100%;
+  height: 100%;
+  left: 0;
+  top: 0;
+  opacity: 0;
+  transition: width 1s linear, opacity 0.5s ease 1s;
+}
+
+.asyncButton:active:after {
+  width: 0%;
+  opacity: 1;
+  transition: 0s
+}

src/features/counter/counterSlice.js

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+import { createSlice } from '@reduxjs/toolkit';
+
+export const slice = createSlice({
+  name: 'counter',
+  initialState: {
+    value: 0,
+  },
+  reducers: {
+    increment: state => {
+      // Redux Toolkit allows us to write "mutating" logic in reducers. It
+      // doesn't actually mutate the state because it uses the immer library,
+      // which detects changes to a "draft state" and produces a brand new
+      // immutable state based off those changes
+      state.value += 1;
+    },
+    decrement: state => {
+      state.value -= 1;
+    },
+    incrementByAmount: (state, action) => {
+      state.value += action.payload;
+    },
+  },
+});
+
+export const { increment, decrement, incrementByAmount } = slice.actions;
+
+// The function below is called a thunk and allows us to perform async logic. It
+// can be dispatched like a regular action: `dispatch(incrementAsync(10))`. This
+// will call the thunk with the `dispatch` function as the first argument. Async
+// code can then be executed and other actions can be dispatched
+export const incrementAsync = amount => dispatch => {
+  setTimeout(() => {
+    dispatch(incrementByAmount(amount));
+  }, 1000);
+};
+
+// The function below is called a selector and allows us to select a value from
+// the state. Selectors can also be defined inline where they're used instead of
+// in the slice file. For example: `useSelector((state) => state.counter.value)`
+export const selectCount = state => state.counter.value;
+
+export default slice.reducer;

src/index.css

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+body {
+  margin: 0;
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
+    'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
+    sans-serif;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+code {
+  font-family: source-code-pro, Menlo, Monaco, Consolas, 'Courier New',
+    monospace;
+}

src/index.js

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+import React from 'react';
+import ReactDOM from 'react-dom';
+import './index.css';
+import App from './App';
+import store from './app/store';
+import { Provider } from 'react-redux';
+import * as serviceWorker from './serviceWorker';
+
+ReactDOM.render(
+  <Provider store={store}>
+    <App />
+  </Provider>,
+  document.getElementById('root')
+);
+
+// If you want your app to work offline and load faster, you can change
+// unregister() to register() below. Note this comes with some pitfalls.
+// Learn more about service workers: https://bit.ly/CRA-PWA
+serviceWorker.unregister();

src/logo.svg

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+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><g fill="#764ABC"><path d="M65.6 65.4c2.9-.3 5.1-2.8 5-5.8-.1-3-2.6-5.4-5.6-5.4h-.2c-3.1.1-5.5 2.7-5.4 5.8.1 1.5.7 2.8 1.6 3.7-3.4 6.7-8.6 11.6-16.4 15.7-5.3 2.8-10.8 3.8-16.3 3.1-4.5-.6-8-2.6-10.2-5.9-3.2-4.9-3.5-10.2-.8-15.5 1.9-3.8 4.9-6.6 6.8-8-.4-1.3-1-3.5-1.3-5.1-14.5 10.5-13 24.7-8.6 31.4 3.3 5 10 8.1 17.4 8.1 2 0 4-.2 6-.7 12.8-2.5 22.5-10.1 28-21.4z"/><path d="M83.2 53c-7.6-8.9-18.8-13.8-31.6-13.8H50c-.9-1.8-2.8-3-4.9-3h-.2c-3.1.1-5.5 2.7-5.4 5.8.1 3 2.6 5.4 5.6 5.4h.2c2.2-.1 4.1-1.5 4.9-3.4H52c7.6 0 14.8 2.2 21.3 6.5 5 3.3 8.6 7.6 10.6 12.8 1.7 4.2 1.6 8.3-.2 11.8-2.8 5.3-7.5 8.2-13.7 8.2-4 0-7.8-1.2-9.8-2.1-1.1 1-3.1 2.6-4.5 3.6 4.3 2 8.7 3.1 12.9 3.1 9.6 0 16.7-5.3 19.4-10.6 2.9-5.8 2.7-15.8-4.8-24.3z"/><path d="M32.4 67.1c.1 3 2.6 5.4 5.6 5.4h.2c3.1-.1 5.5-2.7 5.4-5.8-.1-3-2.6-5.4-5.6-5.4h-.2c-.2 0-.5 0-.7.1-4.1-6.8-5.8-14.2-5.2-22.2.4-6 2.4-11.2 5.9-15.5 2.9-3.7 8.5-5.5 12.3-5.6 10.6-.2 15.1 13 15.4 18.3 1.3.3 3.5 1 5 1.5-1.2-16.2-11.2-24.6-20.8-24.6-9 0-17.3 6.5-20.6 16.1-4.6 12.8-1.6 25.1 4 34.8-.5.7-.8 1.8-.7 2.9z"/></g></svg>

src/serviceWorker.js

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+// This optional code is used to register a service worker.
+// register() is not called by default.
+
+// 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 subsequent visits to a page, after all the
+// existing tabs open on the page have been closed, since previously cached
+// resources are updated in the background.
+
+// To learn more about the benefits of this model and instructions on how to
+// opt-in, read https://bit.ly/CRA-PWA
+
+const isLocalhost = Boolean(
+  window.location.hostname === 'localhost' ||
+    // [::1] is the IPv6 localhost address.
+    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}$/
+    )
+);
+
+export function register(config) {
+  if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
+    // The URL constructor is available in all browsers that support SW.
+    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
+    if (publicUrl.origin !== window.location.origin) {
+      // Our service worker won't work if PUBLIC_URL is on a different origin
+      // from what our page is served on. This might happen if a CDN is used to
+      // serve assets; see https://github.com/facebook/create-react-app/issues/2374
+      return;
+    }
+
+    window.addEventListener('load', () => {
+      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
+
+      if (isLocalhost) {
+        // This is running on localhost. Let's check if a service worker still exists or not.
+        checkValidServiceWorker(swUrl, config);
+
+        // 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://bit.ly/CRA-PWA'
+          );
+        });
+      } else {
+        // Is not localhost. Just register service worker
+        registerValidSW(swUrl, config);
+      }
+    });
+  }
+}
+
+function registerValidSW(swUrl, config) {
+  navigator.serviceWorker
+    .register(swUrl)
+    .then(registration => {
+      registration.onupdatefound = () => {
+        const installingWorker = registration.installing;
+        if (installingWorker == null) {
+          return;
+        }
+        installingWorker.onstatechange = () => {
+          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.'
+              );
+
+              // Execute callback
+              if (config && config.onUpdate) {
+                config.onUpdate(registration);
+              }
+            } 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.');
+
+              // Execute callback
+              if (config && config.onSuccess) {
+                config.onSuccess(registration);
+              }
+            }
+          }
+        };
+      };
+    })
+    .catch(error => {
+      console.error('Error during service worker registration:', error);
+    });
+}
+
+function checkValidServiceWorker(swUrl, config) {
+  // Check if the service worker can be found. If it can't reload the page.
+  fetch(swUrl, {
+    headers: { 'Service-Worker': 'script' },
+  })
+    .then(response => {
+      // Ensure service worker exists, and that we really are getting a JS file.
+      const contentType = response.headers.get('content-type');
+      if (
+        response.status === 404 ||
+        (contentType != null && contentType.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, config);
+      }
+    })
+    .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();
+    });
+  }
+}

src/setupTests.js

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+// jest-dom adds custom jest matchers for asserting on DOM nodes.
+// 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';