React App

├── .gitignore ├── README.md ├── package.json ├── public ├── favicon.ico ├── index.html ├── logo192.png ├── logo512.png ├── manifest.json └── robots.txt ├── src ├── App.css ├── App.js ├── App.test.js ├── index.css ├── index.js ├── logo.svg ├── serviceWorker.js └── setupTests.js └── yarn.lock /.gitignore: -------------------------------------------------------------------------------- 1 | # See https://help.github.com/articles/ignoring-files/ for more about ignoring files. 2 | 3 | # dependencies 4 | /node_modules 5 | /.pnp 6 | .pnp.js 7 | 8 | # testing 9 | /coverage 10 | 11 | # production 12 | /build 13 | 14 | # misc 15 | .DS_Store 16 | .env.local 17 | .env.development.local 18 | .env.test.local 19 | .env.production.local 20 | 21 | npm-debug.log* 22 | yarn-debug.log* 23 | yarn-error.log* 24 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # useAutoScroll 2 | 3 | A custom react hook for autoscrolling. Companion repo to [this medium article](https://medium.com/@markgromano31/react-custom-hooks-useautoscroll-d63f17037a2d) 4 | ``` 5 | npm i 6 | npm start 7 | ``` -------------------------------------------------------------------------------- /package.json: -------------------------------------------------------------------------------- 1 | { 2 | "name": "useautoscroll", 3 | "version": "0.1.0", 4 | "private": true, 5 | "dependencies": { 6 | "@testing-library/jest-dom": "^4.2.4", 7 | "@testing-library/react": "^9.3.2", 8 | "@testing-library/user-event": "^7.1.2", 9 | "react": "^16.13.1", 10 | "react-dom": "^16.13.1", 11 | "react-scripts": "3.4.1" 12 | }, 13 | "scripts": { 14 | "start": "react-scripts start", 15 | "build": "react-scripts build", 16 | "test": "react-scripts test", 17 | "eject": "react-scripts eject" 18 | }, 19 | "eslintConfig": { 20 | "extends": "react-app" 21 | }, 22 | "browserslist": { 23 | "production": [ 24 | ">0.2%", 25 | "not dead", 26 | "not op_mini all" 27 | ], 28 | "development": [ 29 | "last 1 chrome version", 30 | "last 1 firefox version", 31 | "last 1 safari version" 32 | ] 33 | } 34 | } 35 | -------------------------------------------------------------------------------- /public/favicon.ico: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/MarkGeeRomano/useAutoScroll/6de0f59806835761c5e29af61af7e942faedb5ab/public/favicon.ico -------------------------------------------------------------------------------- /public/index.html: -------------------------------------------------------------------------------- 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 12 | 13 | 17 | 18 | 27 | React App 28 | 29 | 30 | 31 |

32 | 42 | 43 | 44 | -------------------------------------------------------------------------------- /public/logo192.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/MarkGeeRomano/useAutoScroll/6de0f59806835761c5e29af61af7e942faedb5ab/public/logo192.png -------------------------------------------------------------------------------- /public/logo512.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/MarkGeeRomano/useAutoScroll/6de0f59806835761c5e29af61af7e942faedb5ab/public/logo512.png -------------------------------------------------------------------------------- /public/manifest.json: -------------------------------------------------------------------------------- 1 | { 2 | "short_name": "React App", 3 | "name": "Create React App Sample", 4 | "icons": [ 5 | { 6 | "src": "favicon.ico", 7 | "sizes": "64x64 32x32 24x24 16x16", 8 | "type": "image/x-icon" 9 | }, 10 | { 11 | "src": "logo192.png", 12 | "type": "image/png", 13 | "sizes": "192x192" 14 | }, 15 | { 16 | "src": "logo512.png", 17 | "type": "image/png", 18 | "sizes": "512x512" 19 | } 20 | ], 21 | "start_url": ".", 22 | "display": "standalone", 23 | "theme_color": "#000000", 24 | "background_color": "#ffffff" 25 | } 26 | -------------------------------------------------------------------------------- /public/robots.txt: -------------------------------------------------------------------------------- 1 | # https://www.robotstxt.org/robotstxt.html 2 | User-agent: * 3 | Disallow: 4 | -------------------------------------------------------------------------------- /src/App.css: -------------------------------------------------------------------------------- 1 | .App { 2 | text-align: center; 3 | height: 100vh; 4 | display: flex; 5 | flex-direction: column; 6 | align-items: center; 7 | justify-content: center; 8 | } 9 | 10 | .view-container { 11 | width: 200px; 12 | height: 200px; 13 | border: 1px solid; 14 | } 15 | 16 | .inputs-container { 17 | overflow: scroll; 18 | max-height: 200px; 19 | border: 1px solid; 20 | height: 80%; 21 | } 22 | 23 | .add-input-btn { 24 | display: flex; 25 | cursor: pointer; 26 | align-items: center; 27 | justify-content: center; 28 | flex-direction: column; 29 | height: 20%; 30 | } -------------------------------------------------------------------------------- /src/App.js: -------------------------------------------------------------------------------- 1 | import React, { useState, useRef, useEffect } from 'react'; 2 | import './App.css'; 3 | 4 | function App() { 5 | return ( 6 |

7 | 8 | 9 |

10 | ); 11 | } 12 | 13 | function View() { 14 | const [inputs, setInputs] = useState([]) 15 | const prevLengthRef = useRef(inputs.length) 16 | const containerRef = useRef(null) 17 | 18 | const prevLength = prevLengthRef.current 19 | useEffect(() => { 20 | if (prevLength < inputs.length) { 21 | const container = containerRef.current 22 | container.scrollTop = container.scrollHeight 23 | } 24 | prevLengthRef.current = inputs.length 25 | }, [inputs.length]) 26 | 27 | const addInput = () => { 28 | setInputs(inputs => [ 29 | ...inputs, 30 | { label: `Input number ${inputs.length}` } 31 | ]) 32 | } 33 | 34 | return ( 35 |

36 |

37 | {inputs.map(({ label }) => ( 38 |

39 | {label} 40 | 41 |

42 | ))} 43 |

44 |

45 | Add Input 46 |

47 |

48 | ) 49 | } 50 | 51 | function View2() { 52 | const [dropdowns, setDropdowns] = useState([]) 53 | const containerRef = useAutoScroll(dropdowns.length) 54 | 55 | const addDropdown = () => { 56 | setDropdowns(dropdowns => [ 57 | ...dropdowns, 58 | { label: `Dropdown number ${dropdowns.length}` } 59 | ]) 60 | } 61 | 62 | return ( 63 |

64 |

65 | {dropdowns.map(({ label }) => ( 66 |

67 | {label} 68 | 72 |

73 | ))} 74 |

75 |

76 | Add Input 77 |

78 |

79 | ) 80 | } 81 | 82 | function useAutoScroll(length) { 83 | const element = useRef(null); 84 | const prevLengthRef = useRef(length); 85 | const prevLength = prevLengthRef.current; 86 | useEffect(() => { 87 | prevLengthRef.current = length; 88 | if (prevLength < length && element.current) { 89 | element.current.scrollTop = element.current.scrollHeight; 90 | }; 91 | }, [length]); 92 | 93 | return element; 94 | } 95 | 96 | 97 | export default App; -------------------------------------------------------------------------------- /src/App.test.js: -------------------------------------------------------------------------------- 1 | import React from 'react'; 2 | import { render } from '@testing-library/react'; 3 | import App from './App'; 4 | 5 | test('renders learn react link', () => { 6 | const { getByText } = render(); 7 | const linkElement = getByText(/learn react/i); 8 | expect(linkElement).toBeInTheDocument(); 9 | }); 10 | -------------------------------------------------------------------------------- /src/index.css: -------------------------------------------------------------------------------- 1 | body { 2 | margin: 0; 3 | font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 4 | 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', 5 | sans-serif; 6 | -webkit-font-smoothing: antialiased; 7 | -moz-osx-font-smoothing: grayscale; 8 | } 9 | 10 | code { 11 | font-family: source-code-pro, Menlo, Monaco, Consolas, 'Courier New', 12 | monospace; 13 | } 14 | -------------------------------------------------------------------------------- /src/index.js: -------------------------------------------------------------------------------- 1 | import React from 'react'; 2 | import ReactDOM from 'react-dom'; 3 | import './index.css'; 4 | import App from './App'; 5 | import * as serviceWorker from './serviceWorker'; 6 | 7 | ReactDOM.render( 8 | 9 | 10 | , 11 | document.getElementById('root') 12 | ); 13 | 14 | // If you want your app to work offline and load faster, you can change 15 | // unregister() to register() below. Note this comes with some pitfalls. 16 | // Learn more about service workers: https://bit.ly/CRA-PWA 17 | serviceWorker.unregister(); 18 | -------------------------------------------------------------------------------- /src/logo.svg: -------------------------------------------------------------------------------- 1 | 8 | -------------------------------------------------------------------------------- /src/serviceWorker.js: -------------------------------------------------------------------------------- 1 | // This optional code is used to register a service worker. 2 | // register() is not called by default. 3 | 4 | // This lets the app load faster on subsequent visits in production, and gives 5 | // it offline capabilities. However, it also means that developers (and users) 6 | // will only see deployed updates on subsequent visits to a page, after all the 7 | // existing tabs open on the page have been closed, since previously cached 8 | // resources are updated in the background. 9 | 10 | // To learn more about the benefits of this model and instructions on how to 11 | // opt-in, read https://bit.ly/CRA-PWA 12 | 13 | const isLocalhost = Boolean( 14 | window.location.hostname === 'localhost' || 15 | // [::1] is the IPv6 localhost address. 16 | window.location.hostname === '[::1]' || 17 | // 127.0.0.0/8 are considered localhost for IPv4. 18 | window.location.hostname.match( 19 | /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/ 20 | ) 21 | ); 22 | 23 | export function register(config) { 24 | if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) { 25 | // The URL constructor is available in all browsers that support SW. 26 | const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href); 27 | if (publicUrl.origin !== window.location.origin) { 28 | // Our service worker won't work if PUBLIC_URL is on a different origin 29 | // from what our page is served on. This might happen if a CDN is used to 30 | // serve assets; see https://github.com/facebook/create-react-app/issues/2374 31 | return; 32 | } 33 | 34 | window.addEventListener('load', () => { 35 | const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`; 36 | 37 | if (isLocalhost) { 38 | // This is running on localhost. Let's check if a service worker still exists or not. 39 | checkValidServiceWorker(swUrl, config); 40 | 41 | // Add some additional logging to localhost, pointing developers to the 42 | // service worker/PWA documentation. 43 | navigator.serviceWorker.ready.then(() => { 44 | console.log( 45 | 'This web app is being served cache-first by a service ' + 46 | 'worker. To learn more, visit https://bit.ly/CRA-PWA' 47 | ); 48 | }); 49 | } else { 50 | // Is not localhost. Just register service worker 51 | registerValidSW(swUrl, config); 52 | } 53 | }); 54 | } 55 | } 56 | 57 | function registerValidSW(swUrl, config) { 58 | navigator.serviceWorker 59 | .register(swUrl) 60 | .then(registration => { 61 | registration.onupdatefound = () => { 62 | const installingWorker = registration.installing; 63 | if (installingWorker == null) { 64 | return; 65 | } 66 | installingWorker.onstatechange = () => { 67 | if (installingWorker.state === 'installed') { 68 | if (navigator.serviceWorker.controller) { 69 | // At this point, the updated precached content has been fetched, 70 | // but the previous service worker will still serve the older 71 | // content until all client tabs are closed. 72 | console.log( 73 | 'New content is available and will be used when all ' + 74 | 'tabs for this page are closed. See https://bit.ly/CRA-PWA.' 75 | ); 76 | 77 | // Execute callback 78 | if (config && config.onUpdate) { 79 | config.onUpdate(registration); 80 | } 81 | } else { 82 | // At this point, everything has been precached. 83 | // It's the perfect time to display a 84 | // "Content is cached for offline use." message. 85 | console.log('Content is cached for offline use.'); 86 | 87 | // Execute callback 88 | if (config && config.onSuccess) { 89 | config.onSuccess(registration); 90 | } 91 | } 92 | } 93 | }; 94 | }; 95 | }) 96 | .catch(error => { 97 | console.error('Error during service worker registration:', error); 98 | }); 99 | } 100 | 101 | function checkValidServiceWorker(swUrl, config) { 102 | // Check if the service worker can be found. If it can't reload the page. 103 | fetch(swUrl, { 104 | headers: { 'Service-Worker': 'script' }, 105 | }) 106 | .then(response => { 107 | // Ensure service worker exists, and that we really are getting a JS file. 108 | const contentType = response.headers.get('content-type'); 109 | if ( 110 | response.status === 404 || 111 | (contentType != null && contentType.indexOf('javascript') === -1) 112 | ) { 113 | // No service worker found. Probably a different app. Reload the page. 114 | navigator.serviceWorker.ready.then(registration => { 115 | registration.unregister().then(() => { 116 | window.location.reload(); 117 | }); 118 | }); 119 | } else { 120 | // Service worker found. Proceed as normal. 121 | registerValidSW(swUrl, config); 122 | } 123 | }) 124 | .catch(() => { 125 | console.log( 126 | 'No internet connection found. App is running in offline mode.' 127 | ); 128 | }); 129 | } 130 | 131 | export function unregister() { 132 | if ('serviceWorker' in navigator) { 133 | navigator.serviceWorker.ready 134 | .then(registration => { 135 | registration.unregister(); 136 | }) 137 | .catch(error => { 138 | console.error(error.message); 139 | }); 140 | } 141 | } 142 | -------------------------------------------------------------------------------- /src/setupTests.js: -------------------------------------------------------------------------------- 1 | // jest-dom adds custom jest matchers for asserting on DOM nodes. 2 | // allows you to do things like: 3 | // expect(element).toHaveTextContent(/react/i) 4 | // learn more: https://github.com/testing-library/jest-dom 5 | import '@testing-library/jest-dom/extend-expect'; 6 | --------------------------------------------------------------------------------