Javascript Loop await async §

How do you use await/async with a loop (for read in sequence and parallel case)?

Reading in sequence §

If you want to read the files in sequence, you cannot use forEach indeed. Just use a modern for … of loop instead, in which await will work as expected:

async function printFiles () {
  const files = await getFilePaths();
 
  for (const file of files) {
    const contents = await fs.readFile(file, 'utf8');
    console.log(contents);
  }
}

Reading in parallel §

If you want to read the files in parallel, you cannot use forEach indeed. Each of the async callback function calls does return a promise, but you’re throwing them away instead of awaiting them. Just use map instead, and you can await the array of promises that you’ll get with Promise.all:

async function printFiles () {
  const files = await getFilePaths();
 
  await Promise.all(files.map(async (file) => {
    const contents = await fs.readFile(file, 'utf8')
    console.log(contents)
  }));
}

Reference §

javascript - Using async/await with a forEach loop - Stack Overflow