How to remove duplicates from an object array using spread operator

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How to remove duplicates from an object array using spread operator



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
Aug 8 at 8:25





5 Answers
5



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


map


find




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.


filter




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<any>' is not an array type. Use compiler option '--downlevelIteration' to allow iterating of iterators."
– tracer
Aug 8 at 8:49





@tracer Try Array.from instead of [...]
– Nenad Vracar
Aug 8 at 8:55


Array.from


[...]



You could use a Set and filter by unkown id.


Set


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;



You could create a Map by id and then extract values. [...new Map(test.map(item => [item.id, item])).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 8 at 8:53




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)



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






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