Math.random() is not cryptographically secure entropy, and Date.now()
is extremely guessable. If you are worried about someone *wanting* to
cause collisions, then that's not so great.
If you don't care about the IETF, and you are writing your program in
Node, then the simplest approach is something like:
var uuid = crypto.randomBytes(24).toString('base64')
To do it asynchronously (since the crypto ops are a little slow):
crypto.randomBytes(24, function (er, bytes) {
var uuid = bytes.toString('base64')
})
Make the number bigger or smaller to adjust the amount of entropy.
Note that IETF uuids are "only" 16 bytes of entropy, so if you do want
IETF-style uuids, you can do this:
var uuid = crypto.randomBytes(16).toString('hex')
var ietfStyle = uuid.replace(/^(.{8})(.{4})(.{4})(.{4})(.{12})$/,
'$1-$2-$3-$4-$5')
I'm going to be moving npm to just use base64 random bytes for salt
eventually, just never got around to it.
On Mon, Aug 6, 2012 at 4:02 PM, Mark Hahn <m...@hahnca.com> wrote:
> The advantage of starting off with the time is that the UUIDs sort by order
> generated which is useful for DB ids. Coding a time into base 36 is a bit
> dangerous though as it may not sort right at some time in the future. That
> time may be centuries from now, not sure. Sorting by hex is known to be far
> in the future.
>
>
> On Mon, Aug 6, 2012 at 3:56 PM, Mark Hahn <m...@hahnca.com> wrote:
>>
>> FWIW, here is the code to exactly match couchdb.
>>
>> UUID = -> '0' + (new Date().getTime() * 1e3).toString(16) +
>> Math.floor(Math.random() * 1e18).toString(16)
>>
>>
>> On Mon, Aug 6, 2012 at 3:43 PM, Rick Waldron <waldron.r...@gmail.com>
>> wrote:
>>>
>>> On Mon, Aug 6, 2012 at 6:28 PM, Mark Hahn <m...@hahnca.com> wrote:
>>>>
>>>> That isn't a hack. It is almost a copy of what couchdb offers. I use
>>>> it all the time.
>>>
>>>
>>> One is an IETF (RFC) and the other isn't.
>>>
>>> http://www.ietf.org/rfc/rfc4122.txt
>>>
>>>>
>>>>
>>>> On Mon, Aug 6, 2012 at 2:17 PM, Ted Young <t...@radicaldesigns.org>
>>>> wrote:
>>>>>
>>>>> Thanks for the feedback, glad to know I found the defacto solution.
>>>>> Tim, that's funny, your hack is more or less what I started with, but I
>>>>> became suspicious that it was too easy somehow. Maybe I'll switch back to
>>>>> that if file-size/performance becomes an issue (which it won't).
>>>>>
>>>>> Ted
>>>>>
>>>>> On Aug 6, 2012, at 8:27 PM, Tim Caswell <t...@creationix.com> wrote:
>>>>>
>>>>> Depending on how strict your requirements are, I often just use:
>>>>>
>>>>> Date.now.toString(36) + "-" + (Math.random() *
>>>>> 0x10000000).toString(36)
>>>>>
>>>>> Date.now is unique every ms and Math.random has a keyspace of 2^32, so
>>>>> collisions are statistically impossible in most practical
>>>>> applications.
>>>>>
>>>>>
>>>>> On Mon, Aug 6, 2012 at 1:01 PM, Rick Waldron <waldron.r...@gmail.com>
>>>>> wrote:
>>>>>
>>>>>
>>>>> On Monday, August 6, 2012 at 1:38 PM, Martin Cooper wrote:
>>>>>
>>>>> On Mon, Aug 6, 2012 at 10:28 AM, Ted Young <t...@radicaldesigns.org>
>>>>> wrote:
>>>>>
>>>>> Hey y'all,
>>>>>
>>>>> So, I have a need for global unique id's. Googling about, I've found
>>>>> the
>>>>> following implementations that seem decent:
>>>>>
>>>>> https://github.com/broofa/node-uuid
>>>>>
>>>>>
>>>>> FWIW, this is the package that npm uses.
>>>>>
>>>>> +1
>>>>>
>>>>> I've been using Robert Keiffer's impl in projects since before it was
>>>>> even
>>>>> on npm—I consider it a "go to"
>>>>>
>>>>> Rick
>>>>>
>>>>>
>>>>> --
>>>>> Martin Cooper
>>>>>
>>>>>
>>>>> https://gist.github.com/1308368
>>>>>
>>>>> Not really sure why I would pick one over the other (besides file
>>>>> size), or
>>>>> if there are any js-specific issues I should be aware of. Any advice?
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Ted
>>>>>
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