How to remove duplicates from an object array using spread operator

Question

I have below object array with id as unique key":

var test = [
  {id: 1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},
  {id: 2, PlaceRef: "*00022", Component: "BAXI10R", SubLocCode: "KIT", BarCode:""},
  {id: 1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},
  {id: 3, PlaceRef: "*00011", Component: "ANR190", SubLocCode: "B1", BarCode: ""}
]

From this I want to retrieve unique objects using spread operator, I have tried using below code:

const uniKeys = [...(new Set(test.map(({ id }) => id)))];

I am able to retrieve id's only, how can I retrieve the unique objects using spread operator. Also, any new ES6 features implementation would be helpful.

This thread: https://gist.github.com/telekosmos/3b62a31a5c43f40849bb has a bunch of ways to get unique values from an array, including for an array of objects (i.e. filtering array of objects on unique values of a certain key). — Jayce444, Aug 08 '18 at 08:25
Maybe helpful - https://stackoverflow.com/a/69815213/11302100 — Nijat Aliyev, Nov 02 '21 at 18:40

score 15 · Accepted Answer · answered Aug 08 '18 at 08:29

You could map back to array of objects using find method, this will return first object with that id.

var test = [{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},{id:2, PlaceRef: "*00022", Component: "BAXI10R", SubLocCode: "KIT", BarCode:""},{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},{id:3, PlaceRef: "*00011", Component: "ANR190", SubLocCode: "B1", BarCode: ""}]
var uniq = [...new Set(test.map(({id}) => id))].map(e => test.find(({id}) => id == e)); 
console.log(uniq)

You could also use filter method instead.

var test = [{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},{id:2, PlaceRef: "*00022", Component: "BAXI10R", SubLocCode: "KIT", BarCode:""},{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},{id:3, PlaceRef: "*00011", Component: "ANR190", SubLocCode: "B1", BarCode: ""}]

var uniq = test.filter(function({id}) {
  return !this[id] && (this[id] = id)
}, {})
 
console.log(uniq)

when i tried first solution it says "Type 'Set' is not an array type. Use compiler option '--downlevelIteration' to allow iterating of iterators." — tracer, Aug 08 '18 at 08:49

score 5 · Answer 2 · answered Aug 08 '18 at 08:40

You could use a Set and filter by unkown id.

var test = [{ id: 1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: "" }, { id: 2, PlaceRef: "*00022", Component: "BAXI10R", SubLocCode: "KIT", BarCode: "" }, { id: 1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: "" }, { id: 3, PlaceRef: "*00011", Component: "ANR190", SubLocCode: "B1", BarCode: "" }],
    unique = test.filter((s => ({ id }) => !s.has(id) && s.add(id))(new Set));
    
console.log(unique);

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score 4 · Answer 3 · answered Aug 08 '18 at 08:29

You could create a Map by id and then extract values. [...new Map(test.map(item => [item.id, item])).values()]

var test = [{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},
{id:2, PlaceRef: "*00022", Component: "BAXI10R", SubLocCode: "KIT", BarCode:""},
{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},
{id:3, PlaceRef: "*00011", Component: "ANR190", SubLocCode: "B1", BarCode: ""}]

console.log([
  ...new Map(test.map(item => [item.id, item])).values()
])

when i tried this it is throwing "Argument of type 'any[][]' is not assignable to parameter of type 'Iterable<[{}, {}]>'" error — tracer, Aug 08 '18 at 08:53

score 2 · Answer 4 · answered Aug 08 '18 at 08:35

var test = [{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},
{id:2, PlaceRef: "*00022", Component: "BAXI10R", SubLocCode: "KIT", BarCode:""},
{id:1, PlaceRef: "*00011", Component: "BATH", SubLocCode: "BAT", BarCode: ""},
{id:3, PlaceRef: "*00011", Component: "ANR190", SubLocCode: "B1", BarCode: ""}];


var uniqArray = Array.from(new Map(test.map(e=>[e.id, e])).values());
console.log(uniqArray)

score 0 · Answer 5 · answered Aug 08 '18 at 08:25

0

Using lodash utility library. you can achieve this. let result = _.uniqBy(test, 'id');

answered Aug 08 '18 at 08:25

Suresh Kumar Ariya

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How to remove duplicates from an object array using spread operator

5 Answers5