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: 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
– Jayce444, Commented Aug 8, 2018 at 8:25

Nenad Vracar · Accepted Answer · 2018-08-08 08:29:53Z

17

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)

answered Aug 8, 2018 at 8:29

Nenad Vracar

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2 Comments

tracer Over a year ago

when i tried first solution it says "Type 'Set<any>' is not an array type. Use compiler option '--downlevelIteration' to allow iterating of iterators."

Nenad Vracar Over a year ago

@tracer Try Array.from instead of [...]

Nina Scholz · Accepted Answer · 2018-08-08 08:40:33Z

6

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);

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

answered Aug 8, 2018 at 8:40

Nina Scholz

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Comments

Yury Tarabanko · Accepted Answer · 2018-08-08 08:29:51Z

4

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()
])

answered Aug 8, 2018 at 8:29

Yury Tarabanko

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1 Comment

tracer Over a year ago

when i tried this it is throwing "Argument of type 'any[][]' is not assignable to parameter of type 'Iterable<[{}, {}]>'" error

Shishir Arora · Accepted Answer · 2018-08-08 08:35:48Z

2

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)

answered Aug 8, 2018 at 8:35

Shishir Arora

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Comments

Suresh Kumar Ariya · Accepted Answer · 2018-08-08 08:25:34Z

0

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

answered Aug 8, 2018 at 8:25

Suresh Kumar Ariya

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