Mongoose/MongoDB result fields appear undefined in Javascript

Question

Is there something that I'm missing that would allow item to log as an object with a parameter, but when I try to access that parameter, it's undefined?

What I've tried so far:

console.log(item) => { title: "foo", content: "bar" } , that's fine
console.log(typeof item) => object
console.log(item.title) => "undefined"

I'll include some of the context just in case it's relevant to the problem.

var TextController = function(myCollection) {
  this.myCollection = myCollection
}

TextController.prototype.list = function(req, res, next) {
  this.myCollection.find({}).exec(function(err, doc) {
    var set = new Set([])
    doc.forEach(function(item) {
      console.log(item)         // Here item shows the parameter
      console.log(item.title)   // "undefined"
      set.add(item.title)       
    })
    res.json(set.get());
  })
}

Based on suggestion I dropped debugger before this line to check what item actually is via the node repl debugger. This is what I found : http://hastebin.com/qatireweni.sm

From this I tried console.log(item._doc.title) and it works just fine.. So, this seems more like a mongoose question now than anything.

There are questions similar to this, but they seem to be related to 'this' accessing of objects or they're trying to get the object outside the scope of the function. In this case, I don't think I'm doing either of those, but inform me if I'm wrong. Thanks

Vincent Bel · Accepted Answer · 2016-04-03 13:26:40Z

57

Solution

You can call the toObject method in order to access the fields. For example:

var itemObject = item.toObject();
console.log(itemObject.title); // "foo"

Why

As you point out that the real fields are stored in the _doc field of the document.

But why console.log(item) => { title: "foo", content: "bar" }?

From the source code of mongoose(document.js), we can find that the toString method of Document call the toObject method. So console.log will show fields 'correctly'. The source code is shown below:

var inspect = require('util').inspect;

...

/**
 * Helper for console.log
 *
 * @api public
 */
Document.prototype.inspect = function(options) {
  var isPOJO = options &&
    utils.getFunctionName(options.constructor) === 'Object';
  var opts;
  if (isPOJO) {
    opts = options;
  } else if (this.schema.options.toObject) {
    opts = clone(this.schema.options.toObject);
  } else {
    opts = {};
  }
  opts.minimize = false;
  opts.retainKeyOrder = true;
  return this.toObject(opts);
};

/**
 * Helper for console.log
 *
 * @api public
 * @method toString
 */

Document.prototype.toString = function() {
  return inspect(this.inspect());
};

answered Apr 3, 2016 at 13:26

Vincent Bel

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4 Comments

George Rappel Over a year ago

Didn't work for me on Mongo 3.2. Says it doesn't have toObject method.

Vincent Bel Over a year ago

@GeorgeRappel By referring the History of Automattic/mongoose, the toObject was added at version 3.4.0. The latest version of mongoose is 4.5.2. I think you need to update your mongoose module...

Enrico Giurin Over a year ago

I have moongose version 4.8.4 and I got the same message error: "TypeError: user.toObject is not a function"

Yuri Aps Over a year ago

If i do this toObject can I use the obj (foo) as a mongoose object normally e.g. foo.save() ? I soved this problem using the .lean() when querying mongoose

Joan-Diego Rodriguez · Accepted Answer · 2015-06-18 20:03:43Z

16

Make sure that you have defined title in your schema:

var MyCollectionSchema = new mongoose.Schema({
    _id: String,
    title: String
});

answered Jun 18, 2015 at 20:03

Joan-Diego Rodriguez

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1 Comment

Aron Over a year ago

This was my problem!!! The document was correct in the database, but because the schema was incorrect it would not display the variable even though it did print the whole object correctly.

plalx · Accepted Answer · 2013-09-10 12:56:00Z

4

Try performing a for in loop over item and see if you can access values.

for (var k in item) {
    console.log(item[k]);
}

If it works, it would mean your keys have some non-printable characters or something like this.

From what you said in the comments, it looks like somehow item is an instance of a String primitive wrapper.

E.g.

var s = new String('test');
typeof s; //object
s instanceof String; //true

To verify this theory, try this:

eval('(' + item + ')').title;

It could also be that item is an object that has a toString method that displays what you see.

EDIT: To identify these issues quickly, you can use console.dir instead of console.log, since it display an interactive list of the object properties. You can also but a breakpoint and add a watch.

edited Sep 10, 2013 at 12:56

answered Sep 10, 2013 at 3:30

plalx

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8 Comments

tippenein Over a year ago

Yes! sort of. Except when I do this, it returns the object as a string. ex "{ title: 'foo'\n content: 'bar'}"

plalx Over a year ago

You mean console.log(item[k]) displays what you said?

tippenein Over a year ago

it displays the item as a string, which makes the parameters of the object inaccessible. I've updated the question to describe better what I know about what's happening.

plalx Over a year ago

@tippenein, I updated the answer so that you understand the result you were getting. I expect that the object had a custom toString function for printing itself. That would explain the confusion.

tippenein Over a year ago

I appreciate the explanations, but judging by my recent finds, item._doc.title returns what I expect. This confirms that it's an object but an object that somehow doesn't print out what it actually contains.

|

George Rappel · Accepted Answer · 2016-06-25 13:49:33Z

4

Use findOne() instead of find().

The find() method returns an array of values, even if you have only one possible result, you'll need to use item[0] to get it.

The findOne method returns one object or none, then you'll be able to access its properties with no issues.

answered Jun 25, 2016 at 13:49

George Rappel

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1 Comment

danefondo Over a year ago

This was it, thank you!!! Missed to notice I was dealing with an array!

user5887278 · Accepted Answer · 2016-02-05 09:06:21Z

3

Old question, but since I had a problem with this too, I'll answer it.
This probably happened because you're using find() instead of findOne(). So in the end, you're calling a method for an array of documents instead of a document, resulting in finding an array and not a single document. Using findOne() will let you get access the object normally.

answered Feb 5, 2016 at 9:06

user5887278

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Comments

Jalasem · Accepted Answer · 2018-02-21 15:47:44Z

A better way to tackle an issue like this is using doc.toObject() like this

doc.toObject({ getters: true })

other options include:

getters: apply all getters (path and virtual getters)
virtuals: apply virtual getters (can override getters option)
minimize: remove empty objects (defaults to true)
transform: a transform function to apply to the resulting document before returning
depopulate: depopulate any populated paths, replacing them with their original refs (defaults to false)
versionKey: whether to include the version key (defaults to true)

so for example you can say

Model.findOne().exec((err, doc) => {
   if (!err) {
      doc.toObject({ getters: true })
      console.log('doc _id:', doc._id) // or title
   }
})

and now it will work

Thomas W · Accepted Answer · 2013-09-10 03:01:14Z

2

You don't have whitespace or funny characters in ' title', do you? They can be defined if you've quoted identifiers into the object/map definition. For example:

var problem = {
    ' title': 'Foo',
    'content': 'Bar'
};

That might cause console.log(item) to display similar to what you're expecting, but cause your undefined problem when you access the title property without it's preceding space.

answered Sep 10, 2013 at 3:01

Thomas W

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1 Comment

tippenein Over a year ago

doc is the results of the mongo db query, so I just iterate through those objects. I did try item[' title'] and item['title '] though. No luck

bertanasco · Accepted Answer · 2014-02-11 04:56:02Z

2

I think using 'find' method returns an array of Documents.I tried this and I was able to print the title

for (var i = 0; i < doc.length; i++) {
   console.log("iteration " + i);
   console.log('ID:' + docs[i]._id);
   console.log(docs[i].title);
}

answered Feb 11, 2014 at 4:56

bertanasco

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Comments

LordRasta · Accepted Answer · 2018-10-23 15:25:22Z

2

If you only want to get the info without all mongoose benefits, save i.e., you can use .lean() in your query. It will get your info quicker and you'll can use it as an object directly.

https://mongoosejs.com/docs/api.html#query_Query-lean

As says in docs, this is the best to read-only scenarios.

answered Oct 23, 2018 at 15:25

LordRasta

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Comments

Valamas · Accepted Answer · 2013-09-10 03:02:37Z

0

Are you initializing your object?

function MyObject()
{
    this.Title = "";
    this.Content = "";
}

var myo1 = new MyObject();

If you do not initialize or have not set a title. You will get undefined.

answered Sep 10, 2013 at 3:02

Valamas

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2 Comments

tippenein Over a year ago

The object is returned by the mongoose collection.find({}), but perhaps you're on to something. Maybe there is something wrong with my initializing of TextController

Valamas Over a year ago

I recommend using chrome or firefox dev tools to place a break point so you can inspect that your object looks like.

Yuri Aps · Accepted Answer · 2022-01-20 20:06:10Z

0

When you make tue query, use .lean() E.g

const order = await Order.findId("84578437").lean()

answered Jan 20, 2022 at 20:06

Yuri Aps

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Comments

arex123 · Accepted Answer · 2022-11-16 04:36:52Z

0

find returns an array of object , so to access element use indexing, like doc[0].title

answered Nov 16, 2022 at 4:36

arex123

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