Most efficient way of handling high volumes of promises?

Question

What is the most efficient way of handling high volumes of promises? I've come up with 2 solutions and determined that Solution 2 (which uses bluebird's promise.map) is faster.

Solution 1 (~38ms per file)

readFile(file) {
  return new Promise((resolve, reject) => {
    jsmediatags.read(file, {
      onSuccess: resolve,
      onError: reject
    })
  })
}

async readFilesHandler() {
  console.time('readFilesHandler timer')
  const fileArray = Array.from(this._fileSelectInput.files)
  const tracksArray = []

  for (let file = 0; file < fileArray.length; file++) {
    await this._readFile(fileArray[file]).then(tags => {
      tracksArray.push({
        id: file + 1,
        title: tags.tags.title || undefined,
        artist: tags.tags.artist || undefined,
        album: tags.tags.album || undefined,
        year: tags.tags.year || undefined
      })
    })
  }
  this.dispatchEvent(new CustomEvent('tracks-selected', {
    detail: tracksArray
  }))
  console.time('readFilesHandler timer') // ~38ms/file
}

Solution 2 (~32ms per file)

_readFiles() {
  console.time('_readFiles timer')
  const fileArray = Array.from(this._fileSelectInput.files)

  window.Promise.map(fileArray, file => {
    return new Promise((resolve, reject) => {
      jsmediatags.read(file, {
        onSuccess: resolve,
        onError: reject
      })
    })
  }, {
    concurrency: 5
  }).then(tags => {
    const results = tags.map((tag, index) => ({
      id: index + 1,
      title: tag.tags.title || undefined,
      artist: tag.tags.artist || undefined,
      album: tag.tags.album || undefined,
      year: tag.tags.year || undefined
    }))
    this.dispatchEvent(new CustomEvent('tracks-selected', {
      detail: results
    }))
  })
  console.timeEnd('_readFiles timer') // ~32ms/file
}

Are there ways of achieving the same result that are even more performant?

Answer 1

You could use Promise.allSettled()

Entire Promise array is resolved as fast as the slowest individual promise is resolved.

const bucket = await Promise.allSettled(fileArray.map(file => this._readFile(file)))

bucket.forEach(file => {
  if (file.value) {
    const tags = file.value;
    tracksArray.push({
      id: file + 1,
      title: tags.tags.title || undefined,
      artist: tags.tags.artist || undefined,
      album: tags.tags.album || undefined,
      year: tags.tags.year || undefined
    })
  }
})