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 3313 times

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Community Evaluations

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?

Auteur anonyme

26/08/2024

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

Auteur anonyme

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.