How can I get unique array from a collection of nested objects with lodash?

Question

I have the following collection:

"items": [{
                "id": 1,
                "title": "Montrachet",
                "imageUrl": "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
                "imageUrls": [
                    "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
                    "http://media.riepenau.com/wines/17973_b.jpg",
                    "http://lorempixel.com/400/400/food/3"         
                ],
                "properties": [
                    {"description" : "Kırmızı Şaraplar Desc"},
                    {"region" :"Bordeaux"},
                    {"age": "16"},
                    {"producer" :"Kayra"},
                    {"grapeType":"Espadeiro"}

                ],
                "priceGlass": "1",
                "priceBottle": "2",
                "year": "1999"

            },

{
                "id": 2,
                "title": "Montrachet2",
                "imageUrl": "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
                "imageUrls": [
                    "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
                    "http://media.riepenau.com/wines/17973_b.jpg",
                    "http://lorempixel.com/400/400/food/3"         
                ],
                "properties": [
                    {"description" : "Kırmızı Şaraplar Desc"},
                    {"region" :"Bordeaux"},
                    {"age": "16"},
                    {"producer" :"Kayra"},
                    {"grapeType":"Chardonnay"}

                ],
                "priceGlass": "1",
                "priceBottle": "2",
                "year": "1999",
            }
]

I want to grab unique grapeTypes from that collection. The returning array shold be ["Chardonnay","Espadeiro"]

What is the best way to do it with lodash?

lodash has method _.uniq which find uniqueness within array. This will work in single, so you need to merge properties and then apply _.uniq with keyword grapeType. — Mithlesh Kumar
– Mithlesh Kumar, Commented Jun 29, 2015 at 11:10

dfsq · Accepted Answer · 2015-06-29 14:07:18Z

2

I think this combination of pluck, map and filter should do it:

var result = _.chain(obj.items).pluck('properties').map(function(obj) {
    return _.filter(obj, function(prop) {
        return prop.grapeType;
    })[0].grapeType;
}).uniq().value();

console.log(result);

Check the demo run below.

// Code goes here

var obj = {
    items: [{
            "id": 1,
            "title": "Montrachet",
            "imageUrl": "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
            "imageUrls": [
                "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
                "http://media.riepenau.com/wines/17973_b.jpg",
                "http://lorempixel.com/400/400/food/3"
            ],
            "properties": [{
                    "description": "Kırmızı Şaraplar Desc"
                }, {
                    "region": "Bordeaux"
                }, {
                    "age": "16"
                }, {
                    "producer": "Kayra"
                }, {
                    "grapeType": "Espadeiro"
                }

            ],
            "priceGlass": "1",
            "priceBottle": "2",
            "year": "1999"

        },

        {
            "id": 2,
            "title": "Montrachet2",
            "imageUrl": "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
            "imageUrls": [
                "http://winebuff.com.hk/products_image/3376-Ramonet-ChassagneMontrachetBlanc.jpg",
                "http://media.riepenau.com/wines/17973_b.jpg",
                "http://lorempixel.com/400/400/food/3"
            ],
            "properties": [{
                    "description": "Kırmızı Şaraplar Desc"
                }, {
                    "region": "Bordeaux"
                }, {
                    "age": "16"
                }, {
                    "producer": "Kayra"
                }, {
                    "grapeType": "Chardonnay"
                }

            ],
            "priceGlass": "1",
            "priceBottle": "2",
            "year": "1999",
        }
    ]
};


var result = _.chain(obj.items).pluck('properties').map(function(obj) {
    return _.filter(obj, function(prop) {
        return prop.grapeType;
    })[0].grapeType;
}).uniq().value();

document.write(JSON.stringify(result));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.8.0/lodash.js"></script>

UPD. If grapeType can be missing from properties then the script should be

var result = _.chain(obj.items).pluck('properties').map(function(obj) {
    return (_.filter(obj, function(prop) {
        return prop.grapeType;
    })[0] || {}).grapeType;
}).compact().uniq().value();

edited Jun 29, 2015 at 14:07

answered Jun 29, 2015 at 10:54

dfsq

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3 Comments

Serhan Oztekin Over a year ago

Thank you for the answer, it works. I wonder what if we didn't have any "properties" array and if we put grapeType like this in the fields; "priceGlass": "1", "priceBottle": "2", "grapeType": "Chardonney"

dfsq Over a year ago

Then it would be just _.chain(obj.items).pluck('grapeType').uniq().value().

Serhan Oztekin Over a year ago

Thank you! One last question; if i have this "properties" array and there's no grapeType field in it, how can i overcome this error message saying "filter(...)[0] is undefined"?

Adam Boduch · Accepted Answer · 2015-06-29 11:20:06Z

0

Here's one way to do it with lodash:

_(items)
    .pluck('properties')
    .map(function(item) {
        return _.find(item, _.ary(_.partialRight(_.has, 'grapeType'), 1));
    })
    .pluck('grapeType')
    .uniq()
    .value();

First, you get the properties arrays using pluck(). Next, you use find() to get the first object in this array that has a grapeType property. This is done using has(), and partially-applying the argument to build the callback function.

Next, you use pluck() again to get the actual property values. Finally, uniq() ensures there are no duplicates.

answered Jun 29, 2015 at 11:20

Adam Boduch

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