Frontend

const createCounter = () => {

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IT One

Kādas iestatījumi ir sīkfailiem (httpOnly, secure, expires, domain, path)?

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IT One

const func = obj.sayHi() const boundFuns = func.bind(obj) boundFuns() ------------------- const submit = (el) => () => { log(el); } arr.map(el => <button onClick={submit(el)}/>) const param = useMemo(() => a + b) return <Child value={param} />

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IT One

Kā jūs saprotat, kas ir renderēšana React? No kā tas var rasties?

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IT One

import React, { useState, useEffect, useRef, useContext, useReducer, useMemo } from 'react'; export default Effects = () => { const [count, setCount] = useState(0); useLayoutEffect(() => console.log("katrs renderings 1")); console.log("katrs renderings 2"); useEffect(() => console.log("katrs renderings 3")); return ( <> <button onClick={() => setCount((prevProps) => ++prevProps)}> Palielināt </button> </> ) }

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IT One

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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IT One

Vai tev ir bijusi pieredze darbā bez analītiķa, kad tev būtu jāizprot uzdevums pats?

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IT One

Kas ir WeakMap?

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IT One

const { foo: bar, bar: foo } = { foo: 1, bar: 2 } console.log(bar) // console.log(foo) //

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IT One

Kā React salīdzina props? Kā darbojas virsmas salīdzinājums?

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IT One

Kam ir paredzēts useRef? Kādas ir tā pielietošanas iespējas?

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IT One

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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IT One

let obj = { a: 1 }; let array = [obj]; obj = null; console.log(obj); // console.log(array); //

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IT One

Tipizē funkciju getParam tā, lai TypeScript pats izceļ objekta īpašības. Padari tipizāciju tādu, lai nebūtu iespējams nodot masīvus.

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IT One

const Effects = () => { const [count, setCount] = useState(0); useLayoutEffect(() => console.log("katrs renderējums 1")); console.log("katrs renderējums 2"); useEffect(() => console.log("katrs renderējums 3")); return ( <> {count} <button onClick={() => setCount((prevProps) => ++prevProps)}> Palielināt </button> </> ); }; export default Effects; // 1 renderējums: // Pēc klikšķa: 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)}> Palielināt </button> </> ); }; export default Effects; // 1 renderējums: // 2 1 3 // Pēc klikšķa: // 2 1 3 // null: // 2 1 3 // // 1: 1, 0 // +: 1, 2 // ++: 2, 2

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IT One

import { useState, useRef, useEffect } from "react"; const useDebugRender = ({props}) => { const prevProp = useRef(props) useEffect(() => { }, []) } const ParentComponent = () => { const [random, setRandom] = useState(0); // Prop kā nodod bērnu komponentam const [text, setText] = useState(""); // Prop kā nodod bērnu komponentam 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); // Šī funkcija tiek nodota kā Prop bērnu komponentam return ( <> <Count: {count} /> <input type="text" onChange={onTextChange} /> <button onClick={createRandom}>Ģenerēt nejauši</button> <div> <ChildComponent random={random} text={text} incrementCount={incrementCount} /> </div> </> ); }; export default ParentComponent;

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IT One

Ja vecāku komponents nodod jaunu masīvu kā props, vai redzēsi jaunus datus ekrānā vai vecos? Kāpēc?

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IT One

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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IT One

Kāpēc debounce, nevis throttle meklēšanai?

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IT One

Vai let un const (hoisting) tiek paceltas? Kas notiek, ja pie tiem piekļūst pirms to deklarēšanas?

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IT One