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

For production purposes you probably want to use a lib like lodasync:

import { filterAsync } from 'lodasync'

const result = await filterAsync(async(element) => {
  await doSomething()
  return element > 3
}, array)

Under the hood, it maps your array by invoking the callback on each element and filters the array using the result. But you should not reinvent the wheel.