Resolve promises one after another (i.e. in sequence)

sequencing-promises.md

asycn/await

async function readFiles(files) {
  for(const file of files) {
    await readFile(file);
  }
};

yield

async function* readFiles(files) {
  for(const file of files) {
    yield await readFile(file);
  }
}

forEach

function readFiles(files) {
  let p = Promise.resolve()
  files.forEach(f => {
    p = p.then(() => readFile(f))
  })
  return p
}

reduce

Or more succinct,

function readFiles(files) {
  return files.reduce((p, f) => {
    return p.then(() => readFile(f))
  }, Promise.resolve())
}