How to use Array.prototype.filter with async?

There is no way to use filter with an async function (at least that I know of).The simplest way that you have to use filter with a collection of promises is to use Promise.all and then apply the function to your collection of results.It would look something like this:

const results = await Promise.all(your_promises)const filtered_results = results.filter(res => //do your filtering here)

Hope it helps.

Adapted from the article How to use async functions with Array.filter in Javascript by Tamás Sallai, you basically have 2 steps:

1. One that creates the conditions for an object to pass
2. One that receives the objects and returns true or false according to conditions

Here's an example

const arr = [1, 2, 3, 4, 5];function sleep(ms) {      return new Promise((resolve) => setTimeout(resolve, ms));    }const asyncFilter = async (arr, predicate) => {    const results = await Promise.all(arr.map(predicate));    return arr.filter((_v, index) => results[index]);}const asyncRes = await asyncFilter(arr, async (i) => {    await sleep(10);    return i % 2 === 0;});console.log(asyncRes);// 2,4

Use Scramjet fromArray/toArray methods...

const result = await scramjet.fromArray(arr)                             .filter(async (item) => somePromiseReturningMethod(item))                             .toArray();

as simple as that - here's a ready example to copy/paste:

const scramjet = require('../../');async function myAsyncFilterFunc(data) {    return new Promise(res => {        process.nextTick(res.bind(null, data % 2));    });}async function x() {    const x = await scramjet.fromArray([1,2,3,4,5])        .filter(async (item) => myAsyncFilterFunc(item))        .toArray();    return x;}x().then(    (out) => console.log(out),    (err) => (console.error(err), process.exit(3)) // eslint-disable-line);

Disclamer: I am the author of scramjet. :)