Waiting for a promise to resolve before function returns a value [duplicate]

Question

I'm trying to execute the following code:

exports.myFunction = function(){
    myPromise.doThis().then(ret => {
     return ret;
    });
}

When calling this function it returns undefined. How do I make the function wait for the promise to resolve then return.

Answer 1

Being asynchronous, there is no guarantee of knowing when the promise will be resolved. It may have to wait for a while (depending on what you are doing).

The typical way of continuing execution after a promise is by chaining execution or by using callback functions.

As a Callback

Your sample code (to me) suggests the use of a callback.

exports.myFunction = function(callback){
    myPromise.doThis().then(ret => {
        callback(ret);
    });
}

Then using would look similar to:

var myFunction = require('pathToFile').myFunction;

myFunction(function(ret){
    //Do what's required with ret here
});

Edit:

As @torazaburo mentioned, the function can be condensed into:

exports.myFunction = function(callback){
    myPromise.doThis().then(callback);
} 

As a Promise

exports.myFunction = function(){
    //Returnes a promise
    return myPromise.doThis();
}

Then using would look similar to:

var myFunction = require('pathToFile').myFunction;

myFunction().then(function(ret){
    //Do what's required with ret here
});