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<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8" />
<linkrel="shortcut icon" href="%PUBLIC_URL%/favicon.ico" />
<metaname="viewport"
content="width=device-width, initial-scale=1, shrink-to-fit=no"
/>
<metaname="theme-color" content="#000000" />
<!-- manifest.json provides metadata used when your web app is installed on a user's mobile device or desktop. See https://developers.google.com/web/fundamentals/web-app-manifest/ --><linkrel="manifest" href="%PUBLIC_URL%/manifest.json" />
<!-- 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>My Todo Application</title></head><body><noscript>You need to enable JavaScript to run this app.</noscript><divid="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>
importReactfrom'react';importReactDOMfrom'react-dom';import'./index.css';importAppfrom'./App';import*asserviceWorkerfrom'./serviceWorker';ReactDOM.render(<App/>,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-PWAserviceWorker.unregister();
import React, {Component} from 'react'
import './Counter.css'
class Counter extends Component {
//Define the initial state in a constructor
//state => counter 0
constructor() {
super(); //Error 1
this.state = {
counter : 0
}
this.increment = this.increment.bind(this);
}
render() {
return (
<div className="counter">
<button onClick={this.increment} >+1</button>
<span className="count">{this.state.counter}</span>
</div>
)
}
increment() { //Update state - counter++
//console.log('increment');
//this.state.counter++; //Bad Practice
this.setState({
counter: this.state.counter + 1
});
}
}
export default Counter
/frontend/todo-app/src/App.test.js
importReactfrom'react';importReactDOMfrom'react-dom';importAppfrom'./App';it('renders without crashing',()=>{constdiv=document.createElement('div');ReactDOM.render(<App/>,div);ReactDOM.unmountComponentAtNode(div);});
/frontend/todo-app/src/serviceWorker.js
// 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-PWAconstisLocalhost=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}$/));exportfunctionregister(config){if(process.env.NODE_ENV==='production'&&'serviceWorker'innavigator){// The URL constructor is available in all browsers that support SW.constpublicUrl=newURL(process.env.PUBLIC_URL,window.location.href);if(publicUrl.origin!==window.location.origin){// Our service worker won't work if PUBLIC_URL is on a different origin// from what our page is served on. This might happen if a CDN is used to// serve assets; see https://github.com/facebook/create-react-app/issues/2374return;}window.addEventListener('load',()=>{constswUrl=`${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 workerregisterValidSW(swUrl,config);}});}}functionregisterValidSW(swUrl,config){navigator.serviceWorker.register(swUrl).then(registration=>{registration.onupdatefound=()=>{constinstallingWorker=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 callbackif(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 callbackif(config&&config.onSuccess){config.onSuccess(registration);}}}};};}).catch(error=>{console.error('Error during service worker registration:',error);});}functioncheckValidServiceWorker(swUrl,config){// 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.constcontentType=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.');});}exportfunctionunregister(){if('serviceWorker'innavigator){navigator.serviceWorker.ready.then(registration=>{registration.unregister();});}}
importReact,{Component}from'react';importFirstComponentfrom'./components/learning-examples/FirstComponent'importSecondComponentfrom'./components/learning-examples/SecondComponent'importThirdComponentfrom'./components/learning-examples/ThirdComponent'importCounterfrom'./components/counter/Counter'import'./App.css';classAppextendsComponent{render(){return(<divclassName="App"><Counter/></div>);}}classLearningComponentsextendsComponent{render(){return(<divclassName="LearningComponents">
My Hello World
<FirstComponent></FirstComponent><SecondComponent></SecondComponent><ThirdComponent></ThirdComponent></div>);}}exportdefaultApp;