Javascript change to variable inside .then not found outside

Question

Below is the code I'm trying to execute.

as described on the comment. I'm trying to have the updates to array 1 to be visible outside of .then() function.

can someone please help me understand why it happens? and how to have it visible outside of .then() function?

Thanks alot !

var array1 = [];    

array2.forEach(function(item) {
    // this is an async all to db.collection.findOne({_id: item.id});
    object = getObject(item.id);
    object.then(function(object) {
        array1.push(object);

        //if I print console.log(array1) here, I can see it getting updated
    });
});

// this does not print anything
console.log(array1)

***EDIT

Though it was a duplicate of existing question, I was able to resolve the issue with provided example below

var array1 = [];    

objectPromises = array2.map(item => function(item));

Promise.all(objectPromises).then(objects -> {
    objects.forEach(function(object){
        array1.push(object);
    });

    console.log(array1);
});

Thanks for the help!

`console.log(array1)` gets executed before your code inside `then` callback. This is asynchronous. — Amit Chigadani, Apr 04 '18 at 06:37

score 1 · Accepted Answer · answered Apr 04 '18 at 06:37

1

You'll have to use a .then (or await), but it's not hard to implement:

const allPromises = array2.map(item => getObject(item.id));
Promise.all(allPromises).then(allObjects => {
  // do something with all objects
});

answered Apr 04 '18 at 06:37

CertainPerformance

356,069
52
309
320

Javascript change to variable inside .then not found outside

1 Answers1