Angular - Remove Duplicate Objects from an Array using set

Question

I need to remove all duplicate objects from my array. I know I can do it by using filter or reduce, but I want to use set instead since (if it works) it should be the shortes and cleanest option.

origionalArray

[{type: "A", label: "A", department: "C"},
{type: "B", label: "B", department: "C"},
{type: "B", label: "B", department: "C"}]

Expected output:

[{type: "A", label: "A", department: "C"},
{type: "B", label: "B", department: "C"}]

I tried:

distinctArray = new Set(origionalArray);

But it returns origionalArray. So my guess is it compares the objects by reference. In java i would override the equals method. But as far as I can find it online this can't be done in TS.

Any ideas how I can get this done? Thank you for your help and time.

You may find an answer here: stackoverflow.com/a/29759699/2358409 — uminder
– uminder, Commented Dec 11, 2019 at 9:55

Naseer · Accepted Answer · 2019-12-11 10:21:56Z

1

You can remove duplicate from array in TS by using this.

const expected = new Set();
const unique = arr.filter(item => !expected.has(JSON.stringify(item)) ? expected.add(JSON.stringify(item)) : false);

edited Dec 11, 2019 at 10:21

answered Dec 11, 2019 at 9:58

Naseer

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5 Comments

Niels Ferguson Over a year ago

I tried this, but it gives me the following error: ''TS2568: Type 'Set<{}>' is not an array type. Use compiler option '--downlevelIteration' to allow iterating of iterators.'' Adding "downlevelIteration": true to my tsconfig does not solve the problem. So I tried to use Array.from(new Set(origionalArray). Then the error disapears, but I still get the origionalArray instead of the reduced Array.

Naseer Over a year ago

ok, previous code works only for strings. i've update the answer for object level checks.

Naseer Over a year ago

arr is your original array which is being filtered to remove duplicate entries.

Niels Ferguson Over a year ago

Thanks! Works perfect. I accepted this as the correct awnser :)

Naseer Over a year ago

glad it helps you. happy coding :)

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