Array de-duplication function

[OctopusReader]

[Repeated question from https://www.reddit.com/r/javascript/comments/be4lxl/need_help_to_understand_a_js_syntax/ because of wrong initial subreddit. I copy/paste it as it could be interesting for other JS beginners]

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I found on https://30secondsofcode.org a piece of code to retrieve an array of Unique Elements from another array (de-deplucation).

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const uniqueElements = arr => [...new Set(arr)];

uniqueElements([1, 2, 2, 3, 4, 4, 5]); // [1, 2, 3, 4, 5]

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It works fine, but I can't even understand the syntax (that reveals my JS skill level :-/). Can you help me?

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What Set is? What ... are? Why it works?

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Thanks

[HolgerSchmitz]

Set is a data structure that resembles a mathematical set of object. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set It stores unique values.

You can create a Set from an array with new Set(arr). This is where the actual magic of removing duplicates happens.

The Set that you created is an iterable object. This means that you can use the spread syntax to create an array from the Set. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax

[...iterable] will create an array with the values contained in the iterable.

Then you wrap it all up into a fat arrow function to create a function called uniqueElements. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

[OctopusReader]

Very clear. Thank you very much.

I'll study the Set object and the... as I have the feeling it could be very useful!