JavaScript - access array from outside of function

Question

I have this basic for loop that iterates through a user's followers. I want to console.log the list of followers from outside of this function as I want to compare this array to another another array somewhere else. How do I do this?

    // Run through user's followers
    SC.get('/users/9110252/followings',function(followings) {

    var userFollowings = [];


        for(i = 0; i < followings.collection.length; i++) {         

            userFollowings.push(followings.collection[i].username);           

        }   

    });

    console.log(userFollowings);

You could return userFollowing from the function. Or you could just log it within the function, what's wrong with doing that? — Mark Chorley, May 06 '16 at 11:10

score 1 · Answer 1 · edited May 23 '17 at 10:33

I guess your SC.get method is asynchronous, and that's why you can't return userfollowings from it.

However, you can put the declaration outside. This won't be enough as the console.log would be evaluated before the end of SC.get. Usually, dealing with asynchronous functions involves promises or callbacks. :

    var userFollowings = [];
        SC.get('/users/9110252/followings').then(function(followings) {
            for(i = 0; i < followings.collection.length; i++) {  
userFollowings.push(followings.collection[i].username); 
            }   

        }).done(function() {
        console.log(userFollowings);
    });

That way, console.log will be evaluated with the right userFollowings array

score 0 · Answer 2 · answered May 06 '16 at 11:11

0

Define the array outside of the function. It can use it thanks to Closure.

var userFollowings = [];

// Run through user's followers
SC.get('/users/9110252/followings',function(followings) {
    for(i = 0; i < followings.collection.length; i++) {         
       userFollowings.push(followings.collection[i].username);           
    }   
});

console.log(userFollowings);

answered May 06 '16 at 11:11

Radek Pech

3,032
1
24
29

2

that can't work if SC.get is asynchronous. console.log will be evaluated before the callback – Regis Portalez May 06 '16 at 11:15
@Regis Portalez: he can still do like `setTimeout(_=>console.log(userFollowings),0)` if he doesn't want to use promises. – Redu May 06 '16 at 12:54
what if SC.get takes 50 ms? it's quite rare http requests answer immediately :) – Regis Portalez May 06 '16 at 12:56
so is it not possible? I'm unsure of where to go from here – mellows May 06 '16 at 15:01
check my answer. you want to have a look on promises and callbacks, depending on what your API makes use of – Regis Portalez May 09 '16 at 08:26

score 0 · Answer 3 · answered May 06 '16 at 11:13

0

Declare var userFollowings = []; outside the function.

var userFollowings = [];
// Run through user's followers
SC.get('/users/9110252/followings',function(followings) 


    for(i = 0; i < followings.collection.length; i++) {         

        userFollowings.push(followings.collection[i].username);           

    }   

});

console.log(userFollowings);

answered May 06 '16 at 11:13

Munawir

3,346
9
33
51

1

that can't work if SC.get is asynchronous. console.log will be evaluated before the callback – Regis Portalez May 06 '16 at 11:16

score 0 · Answer 4 · answered May 06 '16 at 11:22

You can just wrap your code into immediately invoked function and return the needed array:

var userFollowings = function(){ 
    var len = followings.collection.length, userFls = [];
    SC.get('/users/9110252/followings',function(followings) {          
        while (len--) {
            userFls.push(followings.collection[len].username);
        }
    });

    return userFls;
}();

console.log(userFollowings);

JavaScript - access array from outside of function

4 Answers4