Rendering a promise return value with React.useEffect

I’m trying to render the value returned from a promise that calls two external APIs into the JSX.

It seems to work the first time, but then I get undefined.

Am I using useEffect the wrong way?

export default function Dashboard(props) {

    const [pageInfo, setPageInfo] = React.useState();

    async function getPageInfo(props) {

        try {
            const userId = localStorage.getItem('userId');
            let res = await axios.get('http://localhost:8000/user/'+userId);
            let lastPageId =[ - 1];
            let pageInfoObj = await axios.get('http://localhost:8000/page/'+lastPageId);
        } catch (err) {

    React.useEffect(() => {
            .then(data => {
    }, [props]);


>Solution :

use optional chaining or initialize your data as per the response structure and put conditionals

  • If response is an array, initialize with an empty array (so you can map over and get no error’s) and also you can check it’s length before rendering like data.length > 0 &&

  • If response is an object, initialize with null so you can check as data && data.blah

  • If it’s a string then may be an empty string 😛

depends on response structure and it’s not mandatory to have exactly same

why ? because, by the first render still the data i.e., pageInfo is not available yet and it will be undefined as it is not initialized with any value so by default is undefined


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