Question 248948 in Javascript Question posted in
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Javascript – Infinity loop with async function

I need to fetch data from server in infinity loop.
This code generates a reursion, is this correct way?

My code (code updated):

function pause(delay) { return new Promise(r => setTimeout(r, delay)) }
async function fetchData( url, tries = 5 ) {
  try {
    const response = await fetch(url);
    if ( !response.ok )
      throw new Error('Request error');

    const contentType = response.headers.get('content-type');
    if ( !contentType || !contentType.includes('application/json'))
      throw new TypeError('not a JSON')

    const jsonData = await response.json();
    return jsonData;
  } catch(err) {
    console.error('catch error:', err, 'tries left', tries);
    if ( tries == 0 ) throw new Error(err);
    await pause(1500);
    return fetchData( url, tries - 1 );
  }
}

function infinityLoop() {
  fetchData('test.json').then(d => {console.log(d); pause(1000).then( infinityLoop ); });
}
infinityLoop();

updated suggestion (by Dimava), that replace recursion with loop

await function infinityLoop() {
    while ( true ) {
        try {
            let d = await fetchData('test.json');
            console.log(d);
            await pause(1000);
        } catch ( err ) {
            console.error('error:', err);
            break;
        }
    }
    return 0;
}
infinityLoop();
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2

Answers


  1. 0

    You forgot to put a await modifier infront of the fetchData() within the infinityLoop() after that you only need to make the function async aswell.

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  2. 0

    If you want to make an async loop, make an async loop

    async function asyncLoop() {
  while(true) {
    let data = await fetchData('test.json');
    await pause(1000)
  }
}
asyncLoop();
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