What will this component display? ```javascript const MyComponent=()=>{ const[index, setIndex]= useState(1); useEffect(()=>{ setIndex(2); },[]); return {index} ; }; ```

The code will not work because there will be an infinite loop.

Home>IT Tests>Questions>UseState and useEffect in React

Question from the React ⚛️ test

UseState and useEffect in React

Easy

What will this component display?

const MyComponent=()=>{
    const[index, setIndex]= useState(1);

    useEffect(()=>{
        setIndex(2);
    },[]);

    return<div>{index}</div>;
};

Author: Vincent CotroStatus: PublishedQuestion passed 3862 times

Edit

Community Evaluations

Incorrect answer

Madaa

20/01/2025

When we put debugger into this component we can see that this component displays 1 and after first component render useEffect effect has called, effect sets new value component render one more time and only now we see 2 Correct answers are: It will display: 1 and It will display: 2

Ambiguous

Auteur anonyme

15/08/2024

The component will display 1 initially, and then call useEffect which will update the state and then 2 is displayed, so I think the question is ambiguous, it should ask what will it show last?

Dragon parfait

26/08/2024

I think it's not ambiguous to most people. It's classified as very easy because of this.

Rémi

17/09/2024

Effectivement, le cycle de vie du composant est modifié par le useEffect; il affichera "1" au premier rendu, mais il sera executé par la suite (une seule fois vu le tableau de dépendances) et mettra à jour le state, index vaudra alors "2", et donc le composant sera rendu à nouveau.

Madaa

20/01/2025

Yes