how to group JSON objects from array of JSON objects?

Question

Here is an array of JSON objects that has array values that I want to group by (pull unique):

let myArray = [
    {
        "_id": "1",
        "subdata": [
            {
                "subid": "11",
                "name": "A"
            },
            {
                "subid": "12",
                "name": "B"
            }
        ]
    },
    {
        "_id": "2",
        "subdata": [
            {
                "subid": "12",
                "name": "B"
            },
            {
                "subid": "33",
                "name": "E"
            }
        ]
    }
]

Finally I need to get:

[
    {
        "subid": "11",
        "name": "A"
    },
    {
        "subid": "12",
        "name": "B"
    },
    {
        "subid": "33",
        "name": "E"
    }
]

I've tried lodash with no success:

let newArray = lodash.uniqBy(lodash.concat(myArray, 'subdata.subid'), '_id');

Of course I can scan each array element one by one but thought there is easy way to do it with lodash

Ori Drori · Accepted Answer · 2019-11-21 21:35:43Z

Use _.flatMap() to get the an array of all subdata items, and then use _.uniqueBy() with subid:

const myArray = [{"_id":"1","subdata":[{"subid":"11","name":"A"},{"subid":"12","name":"B"}]},{"_id":"2","subdata":[{"subid":"12","name":"B"},{"subid":"33","name":"E"}]}];

const result = _.uniqBy(_.flatMap(myArray, 'subdata'), 'subid');

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

With lodash/fp you can generate a function using _.flow() with the same methods:

const fn = _.flow(
  _.flatMap('subdata'),
  _.uniqBy('subid')
);

const myArray = [{"_id":"1","subdata":[{"subid":"11","name":"A"},{"subid":"12","name":"B"}]},{"_id":"2","subdata":[{"subid":"12","name":"B"},{"subid":"33","name":"E"}]}];

const result = fn(myArray);

console.log(result);

<script src='https://cdn.jsdelivr.net/g/lodash@4(lodash.min.js+lodash.fp.min.js)'></script>

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