Array property in Javascript object is undefined

Question

I'm using Node.js to loop through an array of Artist results I obtain from Mongoose:

User.find({UserType: "Artist"}, '_id Firstname BIO list_artworks').then((artists) =>{
    for (var i=0; i < artists.length; i++){
        console.log(artists[i]);
    }
})

The above code works find and prints out all three properties of Artists that I asked for.

EDIT: Here's an example of what I see in console:

{
    _id: 'T8fdSmf0e1ua',
    BIO: 'This is Susan's bio...\n',
    Firstname: 'Susan',
    list_artworks: [
        'ID ONE',
        'ID TWO', 
        ...
    ]
}

However, when I try to access a property that is an array of Artwork ids, everything is undefined using console.log():

for (var i=0; i < artists.length; i++){
    console.log(artists[i].list_artworks);
}

When I access the other properties of my Artist, like BIO or Firstname, it prints successfully to my console:

for (var i=0; i < artists.length; i++){
    console.log(artists[i].BIO);
}

Why is this the case? I don't think it has to do with async code in this case given that all objects are return in the then() chain. The list_artworks property is clearly there if I print the entire artist object, but why is it undefined when I attempt to access it?

Here's another example. I print out each property, and then the object itself:

console.log(artist.BIO);
console.log("---------------")
console.log(artist.Firstname);
console.log("---------------")
console.log(artist.list_artworks);
console.log("---------------")
console.log(artist)

And here's what is printed on my console:

 
---------------
Mike
---------------
undefined // <--- when I access the property itself
---------------
{
  _id: '599asdsdasd232d23d2',
  Firstname: 'Mike',
  BIO: '',
  list_artworks: // <-- why does it show up here?
   [ '6cohpx7d23asu',
     'W4Fgs23X5aXds',...

Here is my entire code base:

setTimeout(function(){

     User.find({UserType: "Artist"}, '_id Firstname BIO list_artworks').then((artists) =>{
         console.log(artists.length);

        for (var i=0; i < artists.length; i++){
            artist = artists[i];
             console.log(artist.BIO);
             console.log("---------------")
             console.log(artist.Firstname);
             console.log("---------------")
            console.log(artist['list_artworks']);
             console.log("---------------")
             console.log(artist)
            }
        }

     ).catch((err)=>{console.log(err)});
}, constants.NLP_TRAINING_INTERVAL);

Are you sure that all of the objects you're getting from MongoDB have a list_artworks key on them? — Sean Parsons
– Sean Parsons, Commented Jul 8, 2017 at 17:08
@SeanParsons Yes. I edited my question to include my console.log. There's only three Artists objects in my sandbox DB and they all have that key. — Yu Chen
– Yu Chen, Commented Jul 8, 2017 at 17:13
Strange that the output starts with ----------, as that is not the first thing you print... — trincot
– trincot, Commented Jul 8, 2017 at 17:33
@trincot that's because Mike's BIO is empty so it actually did print that line. Just when StackOverflow formatted my output, it cut that text off since it was empty. — Yu Chen
– Yu Chen, Commented Jul 8, 2017 at 17:34
Is there any other code that could have added the list_artwork property later? — trincot
– trincot, Commented Jul 8, 2017 at 17:35

Andy Gaskell · Accepted Answer · 2017-07-08 18:11:22Z

5

Call toObject on the artist:

artist = artists[i].toObject();

answered Jul 8, 2017 at 18:11

Andy Gaskell

31.8k6 gold badges79 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Yu Chen Over a year ago

This works! Thank you! I took a look at the documentation for toObject() but still am not fully sure why this works- isn't calling artists[i] just returning the ith element (an object) of the array?

Andy Gaskell Over a year ago

artists[i] is a mongoose document, not a regular JS object; calling toObject converts the document into an object.

phd · Accepted Answer · 2017-07-09 00:35:31Z

0

Try this:

User.find({UserType: "Artist"}, '_id Firstname BIOlist_artworks').then((artists) =>{
             var index = i.toString();
            console.log(artists[index][‘list_artworks’]);
        }
   }

edited Jul 9, 2017 at 0:35

phd

97.2k14 gold badges165 silver badges223 bronze badges

answered Jul 8, 2017 at 17:55

Frederick Pham

194 bronze badges

1 Comment

Yu Chen Over a year ago

This returns undefined as well.

Shanil Fernando · Accepted Answer · 2017-07-08 17:38:43Z

-1

Try this

User.find({UserType: "Artist"}, '_id Firstname BIO list_artworks').then((artists) =>{

        for (var i=0; i < artists.length; i++){
            console.log(artists[i][‘list_artworks’]);
        }
         }

edited Jul 8, 2017 at 17:38

answered Jul 8, 2017 at 17:35

Shanil Fernando

1,31211 silver badges13 bronze badges

1 Comment

Yu Chen Over a year ago

If you look at my question, I did exactly this and it returns undefined.

Collectives™ on Stack Overflow

Array property in Javascript object is undefined

3 Answers 3

2 Comments

1 Comment

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related