[koolba]

Besides the "Hey I can write stuff you can't read" factor, what's the point of the array and scientific notation here for the UUID generator[1]?

    var uuid = _ =>
      ( [1e7]+-1e3+-4e3+-8e3+-1e11 ).replace( /[018]/g, c =>
        (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
      )

The first piece evaluates to the static string '10000000-1000-4000-8000-100000000000'. Writing it using the array toString and scientific notation saves 8 bytes (or 10 if you remove the other whitespace) but is otherwise pointless.

It'd be even better to use '00000000-0000-4000-0000-000000000000' as the "1" and "8" values aren't special. That would let you replace the /[018]/ with just /0/ too.

[1]: https://github.com/Chalarangelo/30-seconds-of-code/blob/mast...

[onetwotree]

I'm with you 100% that this is silly, show-off-y code golf at its worst. The fact that its purporting to generate something a bit sensitive (why else would you use the awkward `crypto.getRandomValues` interface?) is especially troublesome - sensitive code should be clear at all costs.

I spent a bit longer than 30 seconds looking at it though, and I think the 8 is actually significant - according to the RFC,

> "Set the two most significant bits (bits 6 and 7) of the clock_seq_hi_and_reserved to zero and one, respectively."

The right shift by `c / 4` seems to be taking care of this, at least if JavaScript's shift operator works the way I think it does.

The `1`s are to facilitate the goofy string creation trick.

The fact that there's some discussion around the meaning of the code on HN is a bad thing, of course!