Filtering an array with a function that returns a promise

Question

Given

let arr = [1,2,3];

function filter(num) {
  return new Promise((res, rej) => {
    setTimeout(() => {
      if( num === 3 ) {
        res(num);
         


        

Answer 1

Late to the game but since no one else mentioned it, Bluebird supports Promise.map which is my go-to for filters requiring aysnc processing for the condition,

function filterAsync(arr) {
    return Promise.map(arr, num => {
        if (num === 3) return num;
    })
        .filter(num => num !== undefined)
}