How to use Array.prototype.filter with async?

Question

Background

I am trying to filter an array of objects. Before I filter, I need to convert them to some format, and this operation is asynchronous.

Answer 1

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. :)