Wow I didn't even think about a forEach. Nice.

I like this a lot. Awesome solution.

Object.assign takes two arguments in this case.

The first argument is the target (to which properties will be assigned), in this case Array.prototype
The second argument is a source (from which to assign properties), in this case the methods specified in the instructions (square, cube, sum, etc)

The properties (methods) from the source are applied to the target, and the target is returned. In this case the return value is not necessary but the target ie: Array.prototype is modified (mutated).

This is how many libraries like lodash and others work, "under the hood".

Like this a lot. Brilliant

yes, what

bruh

Why is this voted as a best practice and/or clever?

Nice one. Enjoyed it. 6 kyu IMO

Great kata. Thanks

I'm sure current tests would pass without it but consider the case:
iterable = [undefined, undefined, 'a', 'b', 'c']

Both name (arrayDiff / array_diff) is fine for the tests. Not a kata issue.

Javascript: Tests assert for array_diff, boilerplate names function as arrayDiff, should be array_diff

utils wrapper is useless and should be removed.