mongoose: return only keys from a document

Question

I have a document as follows:

var data={"john:"friend",
          "fruit":"banana",
           "tv":[{"livingroom":"led",
                   "bedroom":"lcd"
                   "fruit":"banana"}]}

and I am trying to return an array of all its unique keys as follows:

["john","fruit,livingroom,bedroom]

so I have the following code:

var mykeys=[];
database.find({},function(result){
    result.forEach(function(each){
         for (key in each){
             mykeys.push(key)
         };
    }});

But this returns a whole bunch of objects I don't need like:

[$__, isNew, errors, _doc, $__original_save, save, _pres, _posts....]

Is there anyway I can get rid of these keys which aren't in the document? I am aware of this mapreduce answer here MongoDB get the names of all the keys in a MongoDB collection but I do not know how to translate it into mongoose. AFAIK mongoose doesn't support runCommand.

Possible duplicate of [MongoDB Get names of all keys in collection](http://stackoverflow.com/questions/2298870/mongodb-get-names-of-all-keys-in-collection) — Bertrand Martel, Jul 31 '16 at 13:38
@Bertrand Martel:I did look at that the solution but it seems too complicated for what I want. I don't need to find unique keys in a collection, just all keys in a document without the vituals. Also I'm not too sure how to implement mapreduce in mongoose. — qts, Jul 31 '16 at 13:45
Do you mean you want to extract keys from one document (any document) from your collection ? — Bertrand Martel, Jul 31 '16 at 13:51
@Bertrand Martel: Actually you're right I am kind of looking for the same thing! But I still don't know how to translate the answer into mongoose. — qts, Jul 31 '16 at 14:26

str · Answer 1 · 2016-07-31T14:12:47.543

8

You have to use the _doc property as this contains your actual document. In addition, you can just use Object.keys to get a list of properties.

var mykeys;
database.findOne({}, function(result) {
    mykeys = Object.keys(result._doc);
});

edited Jul 31 '16 at 14:12

answered Jul 31 '16 at 14:00

str

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This answer works, but I just realised that I have subarrays in my document, which seems to be messing this up :-(. So I have upvoted your answer anyway and edited by question. – qts Jul 31 '16 at 14:26

score 1 · Answer 2 · answered Jan 26 '20 at 20:41

Not sure if you may still need it, but i manged to get it done in Nestjs and Mongoose using this code:

    async leadModel(): Promise<any> {
    const keys = this.leadsModel.findOne();
    return Object.keys(keys.schema.obj)
}

It's still not the best version of it and also throws me a warning that the property doesnt exist on my type, but it works perfectly. Returns only keys of the collection. If you remove Object.keys() it will also return nested keys.

score 0 · Answer 3 · answered Jan 16 '21 at 16:36

0

Adding to @str answer, don't forget to add error as first callback argument

  let tableKeys 
  TRow.findOne({}, (err, result) {
    tableKeys = Object.keys(result._doc);
  });

You might also want to delete '_id' and '__v' from your keys object

answered Jan 16 '21 at 16:36

Ilya Izrailyan

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mongoose: return only keys from a document

3 Answers3

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