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Node.js — Get an Array With Unique Values (Delete Duplicates)

Sometimes you need to remove duplicate values from an array in JavaScript. Actually, it’s straightforward in modern JavaScript to quickly create an array of unique values using the Set data structure.

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JavaScript Array With Unique Values

This is a welcoming use-case for the Set data structure. JavaScript introduced the Set data structure as part of ES2015 describing itself as a collection of unique values.

Here‘s an example extracting the unique values from an array of items:

const items = [1, 2, 3, 2, 3, 1, 5]

const unique = [ ...new Set(items)]  
// [1, 2, 3, 5]

The way it works: create a new set instance of your items which automatically removes the duplicates. Use the spread operator to return the set’s items back into a new array.

You can also use JavaScript’s Array.from() method which creates an array from an iterable. The Set data structure is an iterable object and a valid parameter for this approach:

const items = [1, 2, 3, 2, 3, 1, 5]

const unique = Array.from(new Set(items))  
// [1, 2, 3, 5]

Supercharge Collections

If you’re an avid Node.js developer working a lot with collection pipelines, you may check out the Supercharge Collections package.

This package provides async/await-ready, chainable array utilities:

const Collect = require('@supercharge/collections')

const items = [1, 2, 3, 2, 3, 1, 5]

await Collect(items).unique().all()

// [1, 2, 3, 5]

Which Way Should I Go?

All three methods work totally fine. You may choose whatever you like more.

We like to use Array.from() in simple situations because it reads more explicit, like “create an array from the set of items”.

We use the collections package when in need of a collection pipeline, like mapping, sorting, and filtering besides removing duplicates.

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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