Find unique items of a list in Google Apps Script (JavaScript)

Question

I am working with Google Sheets and I would like to get a list with the unique items of another list. Namely the input is:

List = ['Nick','George','George','Nick','Nick','George','Nick','Alex']

The output will be :

[Nick, George, Alex]

Right now I am using a simple loop to check whether an element appears more than once. But I am sure there is going to be a more clever way.

Jannes Carpentier · Answer 1 · 2020-08-05T18:55:57.330

4

The simplest way is to use a Set. This is defined as a collection that cannot have duplicates

var noduplicates = new Set(List);

You can convert this back to a list if you wish.

var List = ['Nick', 'George', 'George', 'Nick', 'Nick', 'George', 'Nick', 'Alex']

var noduplicates = new Set(List)

noduplicates.forEach(x => console.log(x))

edited Aug 05 '20 at 18:55

answered Aug 05 '20 at 18:47

Jannes Carpentier

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That is even neater than mine! thanks for posting that! Voteup! – soMarios Aug 05 '20 at 19:05
I am not sure if that solution works in Google Apps Scripts though. For some reason new Set returns an empty object. I will check it again and let you know. – soMarios Aug 05 '20 at 19:19
try iterating over it with forEach – Jannes Carpentier Aug 05 '20 at 19:21
The Logger of GAS shows an empty object when you ask it to display the Set. Using forEach returns the values though... newSet.forEach( item => Logger.log(item) ); – Ron Nov 24 '20 at 15:39

score 2 · Accepted Answer · answered Aug 05 '20 at 18:46

The answer is quite straightforward thanks to ES6. You need a combination of filter() and indexOf().

Here is the solution:

var List = ['Nick','George','George','Nick','Nick','George','Nick','Alex']
  
const unique = (value,index,self) =>
{return self.indexOf(value) ===index;}
var Unique_List=List.filter(unique);

Unique_List will give you the desired result.

Output: [Nick, George, Alex]

References:

Find unique items of a list in Google Apps Script (JavaScript)

2 Answers2