Select nested array object and replace it

Question

I got an array (as result of a mongoDB query) with some elements like this:

{ 
    "_id": "ExxTDXJSwvRbLdtpg",
    "content": [
        {
            "content": "First paragraph", 
            "language":"en", 
            "timestamp":1483978498 
        },
        {
            "content": "Erster Abschnitt", 
            "language":"de", 
            "timestamp":1483978498 
        }
    ]
}

But I need to get just a single content field for each data array element, which should be selected by the language. So the result should be (assuming selecting the english content):

{ 
    "_id": "ExxTDXJSwvRbLdtpg",
    "content": "First paragraph"
}

instead of getting all the content data...

I tried to do it with find(c => c.language === 'en), but I don't know how to use this for all elements of the data array. Maybe it is also possible to get the data directly as a mongodb query??

Nina Scholz · Accepted Answer · 2017-01-15 14:35:36Z

3

You could iterate the array and replace the value inside.

var array = [{ _id: "ExxTDXJSwvRbLdtpg", content: [{ content: "First paragraph", language: "en", timestamp: 1483978498 }, { content: "Erster Abschnitt", language: "de", timestamp: 1483978498 }] }];

array.forEach(a => a.content = a.content.find(c => c.language === 'en').content);

console.log(array);

Version with check for content

var array = [{ _id: "ExxTDXJSwvRbLdtpg", content: [{ content: "First paragraph", language: "en", timestamp: 1483978498 }, { content: "Erster Abschnitt", language: "de", timestamp: 1483978498 }] }, { _id: "no_content" }, { _id: "no_english_translation", content: [{ content: "Premier lot", language: "fr", timestamp: 1483978498 }, { content: "Erster Abschnitt", language: "de", timestamp: 1483978498 }] }];

array.forEach(function (a) {
    var language;
    if (Array.isArray(a.content)) {
        language = a.content.find(c => c.language === 'en');
        if (language) {
            a.content = language.content;
        } else {
            delete a.content;
        }
    }
});

console.log(array);

edited Jan 15, 2017 at 14:35

answered Jan 15, 2017 at 13:32

Nina Scholz

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2 Comments

user3142695 Over a year ago

Would this work for documents with missing content field? Because not every element has a content field.

Nina Scholz Over a year ago

what should happen then?

kkkkkkk · Accepted Answer · 2017-01-15 13:43:22Z

3

Given that _id and language are input variables, then you could use this aggregate command to get the expected result:

db.collection.aggregate([{
  $match: {
    _id: _id,
  }
}, {
  $unwind: '$content'
}, {
  $match: {
    'content.language': language,
  }
}, {
  $project: {
    _id: 1,
    content: '$content.content'
  }
}])

answered Jan 15, 2017 at 13:43

kkkkkkk

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2 Comments

user3142695 Over a year ago

I'm using meteor and I think aggregate won't work with that :-(

kkkkkkk Over a year ago

oh, I am a Meteor dev too :) you could use aggregation in server with this package meteorhacks:aggregate

rasmeister · Accepted Answer · 2017-01-15 14:02:32Z

1

var aobjs = [{
  "_id": "ExxTDXJSwvRbLdtpg",
  "content": [
    {
      "content": "First paragraph",
      "language":"en",
      "timestamp":1483978498
    },
    {
      "content": "Erster Abschnitt",
      "language":"de",
      "timestamp":1483978498
    }
  ]
}];

var result = aobjs.map(o => ({ id: o._id, content: o.content.find(c => c.language === 'en').content }));

This returns an object for each with just id and content. In this example, result would be:

[ { id: 'ExxTDXJSwvRbLdtpg', content: 'First paragraph' } ]

answered Jan 15, 2017 at 14:02

rasmeister

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