How to remove duplicates objects from array in javascript?

Question

In my code i have created one array called array1. In this array i have listed multiple objects. I want to filter out array1 objects values as unique and need to group ids with their respective values. I have added my code here,

Array1

var array1 = [
            {
                value:"A",
                id:1
            },
            {
                value:"B",
                id:1
            },
            {
                value:"C",
                id:2
            },
            {
                value:"B",
                id:5
            },
            {
                value:"A",
                id:2
            },
            {
                value:"A",
                id:1
            }
        ];

the result which i want,

[
            {
                group:"A",
                groupIds:[1, 2]
            },
            {
                group:"B",
                groupIds:[1, 5]
            },
            {
                group:"C",
                groupIds:[2]
            }
        ]

Have you searched SO? There's some similar questions: stackoverflow.com/questions/24919074/…, stackoverflow.com/questions/12873228/javascript-group-by-array, stackoverflow.com/questions/14446511/… — Ricardo Pontual
– Ricardo Pontual, Commented Dec 30, 2016 at 12:01
I searched and tried too. But the result which i added in my question is not coming like that — Sathya
– Sathya, Commented Dec 30, 2016 at 12:04

Nina Scholz · Accepted Answer · 2016-12-30 12:04:50Z

4

In plain Javascript, you could use a hash table and Array#indexOf for unique values.

var array = [{ value: "A", id: 1 }, { value: "B", id: 1 }, { value: "C", id: 2 }, { value: "B", id: 5 }, { value: "A", id: 2 }, { value: "A", id: 1 }],
    grouped = array.reduce(function (hash) {
        return function (r, a) {
            if (!hash[a.value]) {
                hash[a.value] = { group: a.value, groupIds: [] };
                r.push(hash[a.value]);
            }
            if (hash[a.value].groupIds.indexOf(a.id) === -1) {
                hash[a.value].groupIds.push(a.id);
            }
            return r;
        };
    }(Object.create(null)), []);

console.log(grouped);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Dec 30, 2016 at 12:04

Nina Scholz

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Nenad Vracar · Accepted Answer · 2016-12-30 12:07:00Z

2

You can use forEach() to group objects by values and Set() to remove duplicate ids from groupIds

var array1 = [{"value":"A","id":1},{"value":"B","id":1},{"value":"C","id":2},{"value":"B","id":5},{"value":"A","id":2},{"value":"A","id":1}]

var result = [];
array1.forEach(function(e) {
  if(!this[e.value]) (this[e.value] = {group: e.value, groupIds: []}) && result.push(this[e.value])
  this[e.value].groupIds = [...new Set(this[e.value].groupIds.concat(e.id))]
}, {})

console.log(result)

answered Dec 30, 2016 at 12:07

Nenad Vracar

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Liron Bar · Accepted Answer · 2018-04-23 13:37:37Z

2

_.uniqBy(objects, function (object) {
  return object.id;
});

that will do :)

answered Apr 23, 2018 at 13:37

Liron Bar

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Comments

Adam Boduch · Accepted Answer · 2016-12-30 13:12:54Z

1

Using lodash:

_(array1)
  .uniqWith(_.isEqual)
  .groupBy('value')
  .map((v, k) => ({ group: k, groupIds: _.map(v, 'id')}))
  .value()

uniqWith() uses isEqual() to remove duplicates. You want to use this approach so that the id and the value props are compared.
groupBy() creates an object whose keys are the value property. Since there are three unique values in the initial array, this object should have three keys.
map() turns the object back into an array, with the expected group and groupIds properties.

answered Dec 30, 2016 at 13:12

Adam Boduch

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Comments

stasovlas · Accepted Answer · 2016-12-30 12:23:45Z

0

use _.groupBy and _.mapValues to iterate object values

var res = _.chain(array1)
    .groupBy('value')
    .mapValues(function(val, key) {
        return {
            group: key,
            groupIds: _.chain(val).map('id').uniq().value()
        };
    })
    .values()
    .value();

answered Dec 30, 2016 at 12:23

stasovlas

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seisei · Accepted Answer · 2016-12-30 12:30:49Z

0

Here's another in plain Javascript.

var hash = {}
array1.forEach( function(e) { 
    hash[e.value] = hash[e.value] || []; 
    if (hash[e.value].indexOf(e.id) == -1) { hash[e.value].push(e.id) }
})
var result = Object.keys(hash).map( function(key) { 
    return { group: key, groupIds: hash[key] } 
})

answered Dec 30, 2016 at 12:30

seisei

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