Aké nastavenia majú cookies (httpOnly, secure, expires, domain, path)?
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Ako rozumieš tomu, čo je render v Reacte? Z čoho to môže nastať?
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Mal si skúsenosť s prácou bez analytika, keď si musel sám pochopiť úlohu?
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import React, { useState, useEffect, useRef, useContext, useReducer, useMemo } from 'react'; export default Effects = () => { const [count, setCount] = useState(0); useLayoutEffect(() => console.log("každé vykreslenie 1")); console.log("každé vykreslenie 2"); useEffect(() => console.log("každé vykreslenie 3")); return ( <> <button onClick={() => setCount((prevProps) => ++prevProps)}> Zvýšiť </button> </> ) }
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const createCounter = () => {
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Čo je WeakMap?
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const obj = [{ value: 1, elems: [ { value: 2, elems: [ { value: 3 }, { value: 6 }, ... ] }, { value: 4, elems: [ { value: 5, elems: [ { value: 6 }, ... ]} ] } ] }] ------------- setTimeout(() => { console.log(1); }, 0); const p = new Promise(resolve => { console.log(2); resolve(); }); p.then(() => { console.log(3) }).then(() => { console.log(4); }); console.log(5);
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const { foo: bar, bar: foo } = { foo: 1, bar: 2 } console.log(bar) // console.log(foo) //
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Ako React porovnáva props? Ako funguje povrchové porovnanie?
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Povedaj mi o Event Loop: ako funguje, čo sú mikroúlohy a makroúlohy?
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Na čo je potrebný useRef? Aké má použitia?
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const { foo: bar, bar: foo } = { foo: 1, bar: 2 }; //foo //bar setTimeout(() => { console.log("timeOut"); }, 0); console.log(1); new Promise((resolve) => { console.log("Promise"); setTimeout(() => { console.log("timeOut2"); resolve(); }, 0); }) .then(() => { console.log("then1"); }) .then(() => { console.log("then2"); }); console.log(4); setTimeout(() => { console.log("timeOut3"); }, 0);
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const Effects = () => { const [count, setCount] = useState(0); useLayoutEffect(() => console.log("vsako ponovno risanje 1")); console.log("vsako ponovno risanje 2"); useEffect(() => console.log("vsako ponovno risanje 3")); return ( <> {count} <button onClick={() => setCount((prevProps) => ++prevProps)}> Povečaj </button> </> ); }; export default Effects; // 1 ponovno risanje: // Po kliku: const Effects = () => { const [count, setCount] = useState(0); const [number, setNumber] = useState(0); useEffect(() => { console.log(count); return () => { console.log(count); }; }); return ( <> {count} <button onClick={() => setCount((prevProps) => ++prevProps)}> Povečaj </button> </> ); }; export default Effects; // 1 ponovno risanje: // 2 1 3 // Po kliku: // 2 1 3 // null: // 2 1 3 // // 1: 1, 0 // +: 1, 2 // ++: 2, 2
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import { useState, useRef, useEffect } from "react"; const useDebugRender = ({props}) => { const prevProp = useRef(props) useEffect(() => { }, []) } const ParentComponent = () => { const [random, setRandom] = useState(0); // Ako Prop se prenosi na dječju komponentu const [text, setText] = useState(""); // Ako Prop se prenosi na dječju komponentu const createRandom = () => setRandom(Math.floor(Math.random() * 100)); const onTextChange = (e) => setText(e.target.value); const [count, setCount] = useState(0); const incrementCount = () => setCount((prev) => prev + 1); // Ova funkcija se prenosi kao Prop na dječju komponentu return ( <> <Count: {count} /> <input type="text" onChange={onTextChange} /> <button onClick={createRandom}>Generiraj nasumično</button> <div> <ChildComponent random={random} text={text} incrementCount={incrementCount} /> </div> </> ); }; export default ParentComponent;
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let obj = { a: 1 }; let array = [obj]; obj = null; console.log(obj); // console.log(array); //
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Typizuj funkciu getParam tak, aby si TypeScript sám zvýraznil prítomnosť vlastností v objekte. Urob typizáciu tak, aby nebolo možné odovzdávať polia.
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Prečo debounce a nie throttle pre vyhľadávanie?
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Ak rodičovský komponent odovzdá nový zoznam ako props, uvidíš nové údaje na obrazovke alebo staré? Prečo?
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const submit = useCallback((el) => () => { log(el); }, []); arr.map(el => <button onClick={submit(el)} />) arr.map(el => <SomeComp key={} onClick={() => submit(el)} />) const param = useMemo(() => ({c: a + b}), [a,b]) return <Child value={param} /> Child = React.memo(() => {})
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Aký je rozdiel medzi await p1, await p2 a Promise.all([p1, p2])?
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