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function Welcome(props) {return <h1>Hello, {props.name}</h1>;}function App() {return (<div><Welcome name="Sara" /><Welcome name="Cahal" /><Welcome name="Edite" /></div>);}ReactDOM.render(<App />,document.getElementById('root'));
const countSubstrings = (str, searchValue) => {let count = 0,i = 0;while (true) {const r = str.indexOf(searchValue, i);if (r !== -1) [count, i] = [count + 1, r + 1];else return count;}};countSubstrings('tiktok tok tok tik tok tik', 'tik'); // 3countSubstrings('tutut tut tut', 'tut'); // 4
const unzipWith = (arr, fn) =>arr.reduce((acc, val) => (val.forEach((v, i) => acc[i].push(v)), acc),Array.from({length: Math.max(...arr.map(x => x.length))}).map(x => [])).map(val => fn(...val));unzipWith([[1, 10, 100],[2, 20, 200],],(...args) => args.reduce((acc, v) => acc + v, 0));// [3, 30, 300]
function formatDate(date) {return date.toLocaleDateString();}function Comment(props) {return (<div className="Comment"><div className="UserInfo"><imgclassName="Avatar"src={props.author.avatarUrl}alt={props.author.name}/><div className="UserInfo-name">{props.author.name}</div></div><div className="Comment-text">{props.text}</div><div className="Comment-date">{formatDate(props.date)}</div></div>);}const comment = {date: new Date(),text: 'I hope you enjoy learning React!',author: {name: 'Hello Kitty',avatarUrl: 'https://placekitten.com/g/64/64',},};ReactDOM.render(<Commentdate={comment.date}text={comment.text}author={comment.author}/>,document.getElementById('root'));
// Orconst randomColor = () => `#${(~~(Math.random()*(1<<24))).toString(16)}`;console.log(randomColor);
const copyToClipboard = str => {const el = document.createElement('textarea');el.value = str;el.setAttribute('readonly', '');el.style.position = 'absolute';el.style.left = '-9999px';document.body.appendChild(el);const selected =document.getSelection().rangeCount > 0? document.getSelection().getRangeAt(0): false;el.select();document.execCommand('copy');document.body.removeChild(el);if (selected) {document.getSelection().removeAllRanges();document.getSelection().addRange(selected);}};copyToClipboard('Lorem ipsum'); // 'Lorem ipsum' copied to clipboard.