How to push a promise's return value into an array?

Question

I'm new to JavaScript so sorry if the question is too dumb.

I have an async function getPartners() in file1.js wich returns an array like this:

return Promise.resolve(partners);
['1','2','3']

In file2.js I have an array with partnerIds and an emptyArray. My goal is when I call getPartners() in file2.js, emptyArray becomes equivalent to the function's return value. In other words I'd like to push the returned values to the emptyArray.

Currently I can get the values this way:

let emptyArray = listItems();
emptyArray.then((result) => {
  console.log(result);
});

My problem is that if I try to console.log(emptyArray) outside of the .then, it's empty. I'd like to filter it too, after getting the values from the promise so I need to save the values into an array which I can call later in the code.

How can I do that?

EDIT: This is what I want to achieve:

const { getPromiseResult } = require('./list');

let existingIds = ['1','2','3'];

let emptyArray = getPromiseResult();
emptyArray.then((resultArrayfromPromise) => {
  console.log(resultArrayfromPromise) // ['2','3','4']
  // filter the results by the existingIds array's elements
  // get result: ['1','2','3','4']
  // and get this result in a new filtered array which I can reach from the outside
});

filteredArray.dosomeotherstuff();

In simple words you can't, read https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call — 1565986223, Apr 14 '19 at 13:17
yes. right. What is it that you're trying to achieve? If you've something specific then there could be (different) ways to solve — 1565986223, Apr 14 '19 at 13:20
My goal is to have an array which contains only those id-s from the promise, which aren't in the partnerIds array. So I need to filter the promise's response array by the partnerId array and get a new filtered array. — Con Troll, Apr 14 '19 at 13:29
@naga-elixir-jar sure, I've updated my original post. Thanks — Con Troll, Apr 14 '19 at 13:38

Mustafa Burak Kalkan · Accepted Answer · 2019-04-14T14:08:10.607

Since ES7, you can use async/await to get rid of then. await waits for operation to complete, and if there is a return value assigns it to the variable.

But you can only use the await in an async function so wrap your codes in it.

async function run() {
    const { listItems } = require('./list');
    let existingIds = ['1','2','3'];
    let emptyArray = await getPromiseresult(); 
    console.log(emptyArray); // now it's not empty
    filteredArray.dosomeotherstuff();
}

run();

How to push a promise's return value into an array?

1 Answers1