initial commit

src/App.css

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+.App {
+  text-align: center;
+}
+
+.App-logo {
+  animation: App-logo-spin infinite 20s linear;
+  height: 80px;
+}
+
+.App-header {
+  background-color: #222;
+  height: 150px;
+  padding: 20px;
+  color: white;
+}
+
+.App-intro {
+  font-size: large;
+}
+
+@keyframes App-logo-spin {
+  from { transform: rotate(0deg); }
+  to { transform: rotate(360deg); }
+}

src/App.js

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+import React, { Component } from 'react';
+import logo from './logo.svg';
+import './App.css';
+
+class App extends Component {
+  render() {
+    return (
+      <div className="App">
+        <div className="App-header">
+          <img src={logo} className="App-logo" alt="logo" />
+          <h2>Welcome to React</h2>
+        </div>
+        <p className="App-intro">
+          To get started, edit <code>src/App.js</code> and save to reload.
+        </p>
+      </div>
+    );
+  }
+}
+
+export default App;

src/App.test.js

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+import React from 'react';
+import ReactDOM from 'react-dom';
+import App from './App';
+
+it('renders without crashing', () => {
+  const div = document.createElement('div');
+  ReactDOM.render(<App />, div);
+});

src/index.css

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+body {
+  margin: 0;
+  padding: 0;
+  font-family: sans-serif;
+}

src/index.js

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+import React from 'react';
+import ReactDOM from 'react-dom';
+import './index.css';
+import App from './App';
+import registerServiceWorker from './registerServiceWorker';
+
+ReactDOM.render(<App />, document.getElementById('root'));
+registerServiceWorker();

src/registerServiceWorker.js

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+// 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) {
+        // Is not local host. Just register service worker
+        registerValidSW(swUrl);
+      } else {
+        // This is running on localhost. Lets check if a service worker still exists or not.
+        checkValidServiceWorker(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();
+    });
+  }
+}