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Sets in Javascript ES6

Damien Cosset on July 11, 2018

Introduction Before ES6, Javascript had no native implementation of Sets. What is a set? A set is a list of values that cannot contain d...
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Nick Taylor •

Thanks for the post Damien. You should do a follow up on Maps, WeakMaps. Maybe go into explaining how Weakmaps are great for meta data.

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Damien Cosset •

Thank for the comment. I'm working on it ;)

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Bernhard Webstudio •

Thanks for the post. The last example is a little confusing to me: When setting obj = null, and afterwards testing with set.has(obj), I would expect the set to return false even if it still contains {} (the object), as the test is equal to set.has(null) and you never added null to the set. Or am I wrong?

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Damien Cosset •

In that last example, we added a reference to the object, inside the variable obj. By setting obj to null, we eliminate the last reference to the object we stored in our set. Therefore, because this is a WeakSet, the object is garbage-collected in order to free memory.

Hope it's clear :)

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Ben Halpern •

Probably the cleanest cover image you've had Damian! 😋

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Mathieu PATUREL •

So, if there are no other references to an object, the reference inside the set will disappear.

I never took the time to actually learn what "weak" things were. Thanks :D