Underscore have some function to extract nested array of objects to new array?

Question

I have:

[{
    "id": 1,
    "listForExtract": [{
        "value1": "1A",
        "value2": "2A"
    }, {
        "value1": "1B",
        "value2": "2B"
    }, ]
},
{
    "id": 2,
    "listForExtract": [{
        "value1": "1C",
        "value2": "2C"
    }, {
        "value1": "1D",
        "value2": "2D"
    }, ]
}]

I want to extract the objects inside listForExtract to a new array like using some function of underscore passing the ID:

something like: _.extractNestedArrayFrom(myArray, 'listForExtract', {'id':2})

[{
    "value1": "1A",
    "value2": "2A"
}, {
    "value1": "1B",
    "value2": "2B"
}]

Lucas.. you can accept any answer below that you find useful.. — Naeem Shaikh
– Naeem Shaikh, Commented Feb 7, 2017 at 16:06

Gruff Bunny · Accepted Answer · 2017-02-07 16:32:54Z

1

You could use where, pluck and flatten:

var result = _.chain(data)
    .where({id:2})
    .pluck('listForExtract')
    .flatten()
    .value()

Where finds all the items in the array that have an id of 2 and pluck extracts the listForExtract. Flatten is then used to flatten the result into one array

edited Feb 7, 2017 at 16:32

answered Feb 7, 2017 at 14:20

Gruff Bunny

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2 Comments

Lucas Over a year ago

Is there a way to return the array rather than array inside another array?

Gruff Bunny Over a year ago

My bad. Added a flatten in there to flatten the array.

Naeem Shaikh · Accepted Answer · 2017-02-07 13:34:53Z

1

You don't even need underscore for that.

Following code should work for you.

myArray.filter(function(){
  return o.id==2
}).map(function(o){
  return o.listForExtract
});

answered Feb 7, 2017 at 13:34

Naeem Shaikh

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2 Comments

Lucas Over a year ago

Is there a way to return the array rather than array inside another array?

Naeem Shaikh Over a year ago

@Lucas.. no matter what u try from underscore.. it will end up with a filter and a map.. so better use that..

Vladu Ionut · Accepted Answer · 2017-02-07 13:39:54Z

1

You can combine map and where methods

var myArray = [{
    "id": 1,
    "listForExtract": [{
        "value1": "1A",
        "value2": "2A"
    }, {
        "value1": "1B",
        "value2": "2B"
    }, ]
},
{
    "id": 2,
    "listForExtract": [{
        "value1": "1C",
        "value2": "2C"
    }, {
        "value1": "1D",
        "value2": "2D"
    }, ]
}];
var result = _.map(_.where(myArray, {
  'id': 2
}), function(elem) {
  return elem.listForExtract
});
console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore.js"></script>

edited Feb 7, 2017 at 13:39

answered Feb 7, 2017 at 13:34

Vladu Ionut

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2 Comments

Lucas Over a year ago

is there a way to return the array rather than array inside another array?

Vladu Ionut Over a year ago

yes try this _.findWhere(myArray, {'id': 2}).listForExtract

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