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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'));
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'));
const arithmeticProgression = (n, lim) =>Array.from({ length: Math.ceil(lim / n) }, (_, i) => (i + 1) * n );arithmeticProgression(5, 25); // [5, 10, 15, 20, 25]
const head = arr => (arr && arr.length ? arr[0] : undefined);head([1, 2, 3]); // 1head([]); // undefinedhead(null); // undefinedhead(undefined); // undefined
//Disclaimer: I do not condone mass web scraping of ESPN websites, and this is just theoretical code that hasn't been used.//Scrape player stats off of https://www.espn.com/nfl/team/roster/_/name/phi/philadelphia-eagles//Example player JS object/*{"shortName": "S. Opeta","name": "Sua Opeta","href": "http://www.espn.com/nfl/player/_/id/3121009/sua-opeta","uid": "s:20~l:28~a:3121009","guid": "dec19157-e984-f981-3724-498281328c97","id": "3121009","height": "6' 4\"","weight": "305 lbs","age": 27,"position": "G","jersey": "78","birthDate": "08/15/96","headshot": "https://a.espncdn.com/i/headshots/nfl/players/full/3121009.png","lastName": "Sua Opeta","experience": 4,"college": "Weber State"}*///The page needs to be focused, so you have to put this code in a bookmarklet and click the page before clicking it. Allegedly.navigator.clipboard.writeText(JSON.stringify(window["__espnfitt__"].page.content.roster.groups.flatMap((group)=>{return group.athletes.map((athlete)=>{//We can assume all football players are above 100 lbs and below 1000 lbs.athlete.weight = parseInt(athlete.weight.substring(0,3));if(athlete.experience == "R") athlete.experience = 0;else athlete.experience = parseInt(athlete.experience);//We can assume players are at least 1 foot, or under 10 feet tall.athlete.inches = 12 * parseInt(athlete.height.substring(0, 1)); //Add feet in inchesathlete.inches += parseInt(athlete.height.substring(2).replaceAll("\"", "").trim()); //Add remaining inchesconst monthDayYear = athlete.birthDate.split("/");athlete.birthMonth = parseInt(monthDayYear[0]);athlete.birthDay = parseInt(monthDayYear[1]);athlete.birthYear = parseInt(monthDayYear[2]);//The only really useful stuff we get from this is Height, weight, left handedness, age, position, and birthdayreturn athlete;});}), null, "\t")).then(null, ()=>{alert("That failed.")});//Changes all the team links on this page https://www.espn.com/nfl/stats/team to the team's roster for easier scraping$$("table > tbody > tr > td > div > div > a").forEach((elm)=>{elm.setAttribute("href", elm.getAttribute("href").replace("team/", "team/roster/"));});
//Retries maxRetries number of times, meaning that if you have 0, then it'll run the function once.async function retryPromise(promiseFn, maxRetries = 3, delayOffset = 0, delayRandomRange = 0) {return new Promise((resolve, reject) => {promiseFn().then(resolve, (error) => { //On errorif (maxRetries <= 0) {return reject(error);} else {if(delayRandomRange * Math.random() + delayOffset < 1.0){return retryPromise(promiseFn, maxRetries - 1, delayOffset, delayRandomRange).then(resolve, reject);}else{return new Promise((resolveTwo, rejectTwo) => {setTimeout(() => {return retryPromise(promiseFn, maxRetries - 1, delayOffset, delayRandomRange).then(resolveTwo, rejectTwo);}, delayRandomRange * Math.random() + delayOffset);}).then(resolve, reject);}}});});}//Tests for that function.//Returns a function that will fail numTimes times, then will return aValuefunction functionThatReturnsAFunctionThatFailsACoupleTimes(numTimes, aValue){return async function(){if(numTimes == 0){return aValue;}numTimes--;throw false;};}const SMALL_NUMBER = 10;function testTest(failNumberOfTimes){let functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(failNumberOfTimes, true);//Test my testfor(let i = 0; i < (failNumberOfTimes * 2); ++i){function evalTest(val){let testTestFailedReason = "";if(val === undefined){testTestFailedReason = "Test test returned undefined for some reason.";}if((i + 1) > failNumberOfTimes){if(val === true){//We're good}else{testTestFailedReason = "Test test didn't return true when it should have.";}}else{if(val === false){//We're good}else{testTestFailedReason = "Test test didn't return false when it should have.";}}testTestFailedReason = testTestFailedReason || "Test test passed test case";console.log(testTestFailedReason, "at index", i, "where the function returned", val);}functionThatFailsACoupleTimes().then(evalTest, evalTest)};}testTest(SMALL_NUMBER);let testCaseCounter = 1;const throwsNoError = [(val)=>{if(val == true){console.log("Passed test case " + (testCaseCounter++));}else{console.error("Unexpected return value", val);}},()=>{console.error("It wasn't supposed to fail!")}]const throwsError = [(val)=>{console.error("It wasn't supposed to succeed!", val);},(val)=>{if(val == false){console.log("Passed test case " + (testCaseCounter++));}else{console.error("Unexpected return value", val);}}];//Runs SMALL_NUMBER times, because SMALL_NUMBER - 1 is the number of retries after the first onelet functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);retryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 1).then(...throwsNoError)functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);//Runs SMALL_NUMBER - 1 times, because SMALL_NUMBER - 2 is the number of retries after the first oneretryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 2).then(...throwsError)//Testing the delay. You'll have to wait a bit too.functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);//Runs SMALL_NUMBER times, because SMALL_NUMBER - 1 is the number of retries after the first oneretryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 1, 500, 500).then(...throwsNoError)functionThatFailsACoupleTimes = functionThatReturnsAFunctionThatFailsACoupleTimes(SMALL_NUMBER - 1, true);//Runs SMALL_NUMBER - 1 times, because SMALL_NUMBER - 2 is the number of retries after the first oneretryPromise(functionThatFailsACoupleTimes, SMALL_NUMBER - 2, 500, 500).then(...throwsError)