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: http://stackoverflow.com/questions/24919074/js-group-array-values-by-groups, http://stackoverflow.com/questions/12873228/javascript-group-by-array, http://stackoverflow.com/questions/14446511/what-is-the-most-efficient-method-to-groupby-on-a-javascript-array-of-objects — Ricardo Pontual, Dec 30 '16 at 12:01
I searched and tried too. But the result which i added in my question is not coming like that — Sathya, Dec 30 '16 at 12:04

score 4 · Answer 1 · answered Dec 30 '16 at 12:04

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; }

score 2 · Accepted Answer · answered Dec 30 '16 at 12:07

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)

score 2 · Answer 3 · answered Apr 23 '18 at 13:37

2

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

that will do :)

answered Apr 23 '18 at 13:37

Liron Bar

21
1

score 1 · Answer 4 · answered Dec 30 '16 at 13:12

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.

score 0 · Answer 5 · answered Dec 30 '16 at 12:23

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();

score 0 · Answer 6 · answered Dec 30 '16 at 12:30

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] } 
})

How to remove duplicates objects from array in javascript?

6 Answers6

Linked