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@jed
Forked from 140bytes/LICENSE.txt
Created May 20, 2011 13:27
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generate random UUIDs

UUID

Returns a random v4 UUID of the form xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where each x is replaced with a random hexadecimal digit from 0 to f, and y is replaced with a random hexadecimal digit from 8 to b.

There's also @LeverOne's approach using iteration, which is one byte shorter.

function b(
a // placeholder
){
return a // if the placeholder was passed, return
? ( // a random number from 0 to 15
a ^ // unless b is 8,
Math.random() // in which case
* 16 // a random number from
>> a/4 // 8 to 11
).toString(16) // in hexadecimal
: ( // or otherwise a concatenated string:
[1e7] + // 10000000 +
-1e3 + // -1000 +
-4e3 + // -4000 +
-8e3 + // -80000000 +
-1e11 // -100000000000,
).replace( // replacing
/[018]/g, // zeroes, ones, and eights with
b // random hex digits
)
}
function b(a){return a?(a^Math.random()*16>>a/4).toString(16):([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g,b)}
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
Version 2, December 2004
Copyright (C) 2011 Jed Schmidt <http://jed.is>
Everyone is permitted to copy and distribute verbatim or modified
copies of this license document, and changing it is allowed as long
as the name is changed.
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. You just DO WHAT THE FUCK YOU WANT TO.
{
"name": "UUID",
"description": "Generates random UUIDs",
"keywords": [
"UUID",
"ID",
"random"
]
}
@jed
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jed commented Feb 9, 2022

That's because it's not part of the spec, it's part of the genius of @subzey. Look at the string that's being replaced

  • 0 and 1 (1 is used as the head of a segment to prevent truncation),
  • 8, which is special cased with the ^ operation to clamp it to the proper values, but not
  • 4, which cannot be replaced because it specifies the version in the spec.

@jed
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jed commented Feb 9, 2022

right, you got it. the 1 could be any other digit, really, it's just a placeholder, but the 8 was selected for its bitwise operation properties.

@jed
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jed commented Feb 9, 2022

(there's a walkthrough here, fwiw)

@getify
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getify commented Feb 9, 2022

@jed thanks! :)

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