How do I access promise callback value outside of the function?

Question

It is to my understanding that callback functions are asynchronous and cannot return a value like regular functions. Upon reading about promises, I thought I grasped a good understanding about them, that they are basically an enhanced version of callbacks that allows returning a value like asynchronous function. In my getConnections method, I am attempting to call the find() function on my database through mongoose, and I am attempting to grab this array of objects and send it to the views.

var test =  new Promise((resolve, reject) => {
        Database.find().then(list => {
            resolve(list);

        }).catch(err=> {
            return reject(err);
        })

        })
console.log(test)

When I attempt to log to the console outside of the promise function, I get Promise { _U: 0, _V: 0, _W: null, _X: null }

I don't think this is functioning correctly, and I thought I utilized promises correctly. Could anyone point me in the right direction on how to return this array of objects outside of the callback function?

Does this answer your question? [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Anurag Srivastava, Apr 17 '20 at 22:31
Try this instead: `test.then(x=> console.log(x));`. [then](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/then) is the normal mechanism to get the result of the promise once it resolves. — David784, Apr 17 '20 at 22:50
Well I get the console log but I want to access this variable outside the document and send it to views. — Calamity, Apr 17 '20 at 23:13
rethink your code ... think like this ... *asynchrony can not be made synchronous, because I'm writing javascript, not developing a time machine* :D — Jaromanda X, Apr 18 '20 at 00:12
*send it to views* sounds something you could wrap into `then()`. — tevemadar, Apr 18 '20 at 08:15
`Database.find().then(list => list)` <-- list is what you need — Deryck, Apr 18 '20 at 13:15

score 3 · Answer 1 · answered Apr 18 '20 at 13:12

3

You can simply add await before the promise declaration. i.e.

var test = await new Promise...

answered Apr 18 '20 at 13:12

Karim A. Wazzan

209
1
5

await can be used only in an async function. Check @Yavor's answer – NiroshanJ May 23 '21 at 06:19

Yavor Daskalov · Answer 2 · 2020-10-09T13:01:38.053

2

The thing is that when you write a function like this:

const getData = async () => { const response = await fetch(someUrl, {}, {}); return response;}

Then you also need to await that function when you call it. Like this:

const setData = async () => { const dataToSet = await getData(); }

edited Oct 09 '20 at 13:01

answered Oct 01 '20 at 15:39

Yavor Daskalov

29
5

score 1 · Answer 3 · answered Apr 18 '20 at 12:40

let test =  new Promise((resolve, reject) => {
        Database.find().then(list => {
            resolve(list);

        }).catch(err=> {
            return reject(err);
        })

        })

test
.then(result=>console.log(result))

Should solve your problem.

Surojit Paul · Answer 4 · 2020-04-18T14:09:42.333

1

    var someValue;
    var test =  await new Promise((resolve, reject) => {
        Database.find().then(list => {
           resolve(list);

         }).catch(err=> {
           return reject(err);
       })

    }).then(res => {
      someValue=res;
    })

   console.log(someValue);

edited Apr 18 '20 at 14:09

answered Apr 18 '20 at 13:28

Surojit Paul

1,232
9
11

How do I access promise callback value outside of the function?

4 Answers4

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