What's the most elegant way in ES6 to filter out duplicates in an array in Javascript

Question

I've seen alot of answers to this topic but I'm not completely satisfied. The snippet I liked the most was this one:

[ ["1", "2"], ["1", "2", "3"], ["1", "2"] ]
  .filter(
    (path: string[], i: number, array: string[][]) => _.findIndex(array, x => _.isEqual(x, path)) === i
  )

This works but I find it waaaayy too verbose for my liking. Isn't there a more compact way to achieve this? Even if it means using lodash or something. I feel I'm missing something really obvious in the year 2019 (nearly 2020).

Questions asking us to suggest, find or recommend a book, tool, software library, plug-in, tutorial, explain a technique or provide any other off-site resource are off-topic for Stack Overflow — Jamie, Nov 26 '19 at 09:45
Dup of https://stackoverflow.com/questions/44014799/javascript-how-to-remove-duplicate-arrays-inside-array-of-arrays — Salman A, Nov 26 '19 at 10:14
Based on the accepted answer looks like it is a not-RTFM problem. — Salman A, Nov 26 '19 at 10:33
I (like many others) looked into lodash documentation but somehow we couldn't find .uniqWith(). Sorry we are not as perfect as you are. — XDS, Nov 26 '19 at 10:40

Nina Scholz · Answer 1 · 2019-11-26T12:22:35.387

1

You could take a bunch of closures and check with a Set and a stringified value.

var array = [["1", "2"], ["1", "2", "3"], ["1", "2"]],
    unique = array.filter(
        (s => a => 
            (j => !s.has(j) && s.add(j))
            (JSON.stringify(a))
        )
        (new Set)    
    );

console.log(unique);

edited Nov 26 '19 at 12:22

answered Nov 26 '19 at 09:58

Nina Scholz

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score 1 · Accepted Answer · answered Nov 26 '19 at 10:22

With lodash you can use _.uniqWith() to deduplicate the array, and use _.isEqual() as the comparator:

const array = [["1", "2"], ["1", "2", "3"], ["1", "2"]]

const result = _.uniqWith(array, _.isEqual)

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>

score -1 · Answer 3 · answered Nov 26 '19 at 09:49

Many ways actually, try to play in browser console. I usually using most straightforward with primitives:

const uniques = [...new Set(originalArray)]

For objects harder:

const uniques = original.reduce((result, object) => {
  if (!result.find((o) => i._id === object._id)) {
    result.push(object);
  }
  return result;
}, [])

What's the most elegant way in ES6 to filter out duplicates in an array in Javascript

3 Answers3