Learn useEffect In 13 Minutes

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Recommends Jesse · 2021-03 · Stack Overflow · on “React: Data not showing until I search”

You are experiencing this is because the default state you have set is a empty array. You did this when you made this definition const [data,setData]=useState([]); So to have some default data you want to call an endpoint to return the default data you want to see using the useEffect [LINK] hook. You can also see it as a mechanism that triggers a side effect as a result of a state change. See a snippet below of what your code should look like. // useEffect(() => { //Initial API call with default results //Set data with API results }, [data]); //data controls when the component updates, so when you call you call the search function, it'll cause a change to the data value and trigger the `useE

Recommends Penny Liu · 2025-02 · Stack Overflow · on “How can I useEffect on screen width change?”

You can refer to Kyle's video at 9:04 [this video] . This video explains it well on how to dynamically update the screen width value [LINK] . It should also return a cleanup function with removeEventListener . const [windowWidth, setWindowWidth] = useState(window.innerWidth); const handleResize = () => { setWindowWidth(window.innerWidth); }; // Update window width useEffect(() => { window.addEventListener('resize', handleResize); // Cleanup return () => window.removeEventListener('resize', handleResize); }, []);

Cites Sameer · 2021-07 · Stack Overflow · on “Switch themes when local storage changes onClick in react”

Update As you wanted to rerender the parent App component, you need to send its update function to the child UserProfilePromoter component as props. //Parent App component export default function App() { const [themeUpdated, setThemeUpdated] = useState(false); const updateAppComponent = () => { setThemeUpdated(!themeUpdated); }; const getClass = () => { return localStorage.getItem('theme'); }; return ( <div className={getClass()}> <h1>Hello StackBlitz!</h1> <Sample updateAppComponent={updateAppComponent} /> </div> ); } //Child sample component export default function Sample(props) { const { updateAppComponent } = props; const [themeToggle, setThemeToggle] = useState(false); const update = ()

Cites Data T · 2022-06 · Stack Overflow · on “Should return run before or after useEffect?”

I'm following this video [this video] to learn useEffect. According to the video the return should run first, then the useEffect itself. However, my useEffect runs before the return. What should be the correct sequence of execution ? my code: import React, { useState, useEffect, useRef } from 'react'; export default function Use_Effect() { const [ val , setVal ] = useState(0) useEffect( () => { console.log('add') return ( console.log('return') ) }, [val] ) return ( <div> <input value={val} onChange={() => { setVal(pre => pre + 1) console.log("main window",{val})}} /> </div> ) } The video says I should get return -> add -> return -> add But I'm getting add -> return -> add -> return Thanks very mu