first react attempts

src/AlternativeBody.js

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+import * as React from "react";
+
+class AlternativeBody extends React.Component{
+    render() {
+        return (
+            <div>Second page!</div>
+        );
+    }
+}
+
+export default AlternativeBody;

src/App.css

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+

src/App.js

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+import React from 'react';
+import './App.css';
+import MainBody from "./MainBody";
+import AlternativeBody from "./AlternativeBody"
+import ReactDOM from 'react-dom';
+import 'bootstrap/dist/css/bootstrap.min.css';
+
+class App extends React.Component {
+    page1click() {
+        console.log("click page1");
+
+        // rerender mainbody space here
+        ReactDOM.render(
+            <MainBody/>,
+            document.getElementById("mainbody")
+        );
+    }
+
+    page2click() {
+        console.log("click page2");
+
+        // rerender mainbody space here
+        ReactDOM.render(
+            <AlternativeBody/>,
+            document.getElementById("mainbody")
+        );
+    }
+
+    render() {
+        return (
+            <div className="App">
+                <nav className="navbar navbar-expand-sm bg-primary navbar-dark">
+                    <a className="navbar-brand" href="!#">Lukis Tube</a>
+
+                    <ul className="navbar-nav">
+                        <li className="nav-item">
+                            <a className="nav-link" onClick={() => this.homePageClick()} href="!#">Home</a>
+                        </li>
+                        <li className="nav-item">
+                            <a className="nav-link" onClick={() => this.homePageClick()} href="!#">Random Video</a>
+                        </li>
+                        <li className="nav-item">
+                            <a className="nav-link" onClick={() => this.homePageClick()} href="!#">Categories</a>
+                        </li>
+                    </ul>
+                </nav>
+                <div>
+                    <button onClick={() => this.page1click()}>Page1</button>
+                    <button onClick={() => this.page2click()}>Page2</button>
+                </div>
+                <div id="mainbody">
+                    mimimimimi
+                </div>
+
+            </div>
+        );
+    }
+
+    homePageClick() {
+        console.log("click page1");
+
+        // rerender mainbody space here
+        ReactDOM.render(
+            <MainBody/>,
+            document.getElementById("mainbody")
+        );
+    }
+}
+
+export default App;

src/MainBody.js

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+import React from "react";
+
+class MainBody extends React.Component {
+    render() {
+        const requestOptions = {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ title: 'React POST Request Example' })
+        };
+        fetch('https://jsonplaceholder.typicode.com/posts', requestOptions)
+            .then(response => response.json())
+            .then(data => this.setState({ postId: data.id }));
+        return (
+            <div>Hey from other class</div>
+        );
+    }
+}
+
+export default MainBody;

src/Zwei.js

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+import React from 'react';
+
+class TodoApp extends React.Component {
+    constructor(props) {
+        super(props);
+        this.state = {items: [], text: ''};
+        this.handleChange = this.handleChange.bind(this);
+        this.handleSubmit = this.handleSubmit.bind(this);
+    }
+
+    render() {
+        return (
+            <div>
+                <h3>TODO</h3>
+                <TodoList items={this.state.items}/>
+                <form onSubmit={this.handleSubmit}>
+                    <label htmlFor="new-todo">
+                        What needs to be done?
+                    </label>
+                    <input
+                        id="new-todo"
+                        onChange={this.handleChange}
+                        value={this.state.text}
+                    />
+                    <button>
+                        Add #{this.state.items.length + 1}
+                    </button>
+                </form>
+            </div>
+        );
+    }
+
+    handleChange(e) {
+        this.setState({text: e.target.value});
+    }
+
+    handleSubmit(e) {
+        e.preventDefault();
+        if (this.state.text.length === 0) {
+            return;
+        }
+        const newItem = {
+            text: this.state.text,
+            id: Date.now()
+        };
+        this.setState(state => ({
+            items: state.items.concat(newItem),
+            text: ''
+        }));
+    }
+}
+
+class TodoList extends React.Component {
+    render() {
+        return (
+            <ul>
+                {this.props.items.map(item => (
+                    <li key={item.id}>{item.text}</li>
+                ))}
+            </ul>
+        );
+    }
+}
+
+export default TodoApp;

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 * as serviceWorker from './serviceWorker';
+
+ReactDOM.render(
+  <React.StrictMode>
+    <App />
+  </React.StrictMode>,
+  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.register();

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();
+      })
+      .catch(error => {
+        console.error(error.message);
+      });
+  }
+}

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';