Créer un GUID / UUID en JavaScript?
https://stackoverflow.com/questions/105034
-
01-07-2019 - |
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J'essaie de créer des identifiants uniques en JavaScript dans le monde entier. Je ne sais pas quelles routines sont disponibles sur tous les navigateurs, comment & "Random &"; et ensemencé le générateur de nombre aléatoire intégré est, etc.
Le GUID / UUID doit comporter au moins 32 caractères et doit rester dans la plage ASCII afin d'éviter tout problème lors de leur transmission.
La solution
UUID (Universally Unique IDentifier), également appelé GUID (Globally Unique IDentifier), selon RFC 4122 , sont des identifiants avec une certaine garantie d'unicité.
Le meilleur moyen de les générer consiste à suivre les instructions de mise en oeuvre de la dite RFC, à utiliser l’une des nombreuses implémentations open source validées par la communauté.
Notez que le fait de générer de manière aléatoire les identifiants octet par octet ou caractère par caractère ne vous donnera pas les mêmes garanties qu'une implémentation conforme. De plus, il est très important que les systèmes fonctionnant avec des UUID conformes puissent choisir de ne pas accepter ceux générés aléatoirement, et de nombreux validateurs open source vérifieront en fait la présence d’une structure valide.
Un UUID doit avoir le format suivant:
xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx
Les positions M et N ne peuvent avoir que certaines valeurs. Pour le moment, les seules valeurs valides pour M sont 1, 2, 3, 4 et 5; ainsi, générer cette position de manière aléatoire rendrait la plupart des résultats inacceptables.
Autres conseils
Pour une solution conforme à la RFC4122 version 4, cette solution one-liner (ish) est le plus compact que je puisse trouver.:
function uuidv4() {
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8);
return v.toString(16);
});
}
console.log(uuidv4())
Mise à jour du 2015-06-02 : sachez que l'unicité des UUID dépend fortement du générateur de nombres aléatoires sous-jacent. La solution ci-dessus utilise Math.random() par souci de brièveté. Cependant, crypto n’est pas garanti d’être un GNA de haute qualité. Voir l'excellent article sur Math.random () d'Adam Hyland pour plus de détails. Pour une solution plus robuste, envisagez quelque chose comme le module uuid [Avertissement: je suis l'auteur] , qui utilise des API RNG de meilleure qualité, le cas échéant.
Mise à jour du 26/08/2015 : Ce remarque gist explique comment déterminer le nombre d'identifiants pouvant être générés avant d'atteindre une certaine probabilité de collision. Par exemple, avec les UUID RFC4122 version 4 3.26x10 15 , vous avez 1 chance sur 1 de collision.
Mise à jour du 2017-06-28 : A bon article de développeurs Chrome sur l'état de la qualité PRNG Math.random dans Chrome, Firefox et Safari. tl; dr - À la fin de 2015, c'est & "plutôt bon &"; mais pas la qualité cryptographique. Pour résoudre ce problème, voici une version mise à jour de la solution ci-dessus, qui utilise ES6, l'API <=> et a peu de magicien de JS je ne peux pas prendre le crédit pour :
function uuidv4() {
return ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, c =>
(c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
)
}
console.log(uuidv4());
J'aime vraiment la réponse claire de Broofa , mais il est regrettable que de mauvaises applications de Math.random laissent la chance à collision.
Voici une solution conforme à la version 4 de la RFC4122 similaire qui résout ce problème en décalant la première 13 nombres hexadécimaux par une partie hexadécimale de l'horodatage. Ainsi, même si <=> se trouve sur la même graine, les deux clients devront générer l'UUID exactement à la même milliseconde (ou 10 000 ans plus tard) pour obtenir le même UUID:
function generateUUID() { // Public Domain/MIT
var d = new Date().getTime();
if (typeof performance !== 'undefined' && typeof performance.now === 'function'){
d += performance.now(); //use high-precision timer if available
}
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
var r = (d + Math.random() * 16) % 16 | 0;
d = Math.floor(d / 16);
return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
});
}
broofa's answer is pretty slick, indeed - impressively clever, really... rfc4122 compliant, somewhat readable, and compact. Awesome!
But if you're looking at that regular expression, those many replace() callbacks, toString()'s and Math.random() function calls (where he's only using 4 bits of the result and wasting the rest), you may start to wonder about performance. Indeed, joelpt even decided to toss out RFC for generic GUID speed with generateQuickGUID.
But, can we get speed and RFC compliance? I say, YES! Can we maintain readability? Well... Not really, but it's easy if you follow along.
But first, my results, compared to broofa, guid (the accepted answer), and the non-rfc-compliant generateQuickGuid:
Desktop Android
broofa: 1617ms 12869ms
e1: 636ms 5778ms
e2: 606ms 4754ms
e3: 364ms 3003ms
e4: 329ms 2015ms
e5: 147ms 1156ms
e6: 146ms 1035ms
e7: 105ms 726ms
guid: 962ms 10762ms
generateQuickGuid: 292ms 2961ms
- Note: 500k iterations, results will vary by browser/cpu.
So by my 6th iteration of optimizations, I beat the most popular answer by over 12X, the accepted answer by over 9X, and the fast-non-compliant answer by 2-3X. And I'm still rfc4122 compliant.
Interested in how? I've put the full source on http://jsfiddle.net/jcward/7hyaC/3/ and on http://jsperf.com/uuid-generator-opt/4
For an explanation, let's start with broofa's code:
'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
return v.toString(16);
});
So it replaces x with any random hex digit, y with random data (except forcing the top 2 bits to 10 per the RFC spec), and the regex doesn't match the - or 4 characters, so he doesn't have to deal with them. Very, very slick.
The first thing to know is that function calls are expensive, as are regular expressions (though he only uses 1, it has 32 callbacks, one for each match, and in each of the 32 callbacks it calls Math.random() and v.toString(16)).
The first step toward performance is to eliminate the RegEx and its callback functions and use a simple loop instead. This means we have to deal with the - and 4 characters whereas broofa did not. Also, note that we can use String Array indexing to keep his slick String template architecture:
function e1() {
var u='',i=0;
while(i++<36) {
var c='xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'[i-1],r=Math.random()*16|0,v=c=='x'?r:(r&0x3|0x8);
u+=(c=='-'||c=='4')?c:v.toString(16)
}
return u;
}
Basically, the same inner logic, except we check for - or 4, and using a while loop (instead of replace() callbacks) gets us an almost 3X improvement!
The next step is a small one on the desktop but makes a decent difference on mobile. Let's make fewer Math.random() calls and utilize all those random bits instead of throwing 87% of them away with a random buffer that gets shifted out each iteration. Let's also move that template definition out of the loop, just in case it helps:
function e2() {
var u='',m='xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx',i=0,rb=Math.random()*0xffffffff|0;
while(i++<36) {
var c=m[i-1],r=rb&0xf,v=c=='x'?r:(r&0x3|0x8);
u+=(c=='-'||c=='4')?c:v.toString(16);rb=i%8==0?Math.random()*0xffffffff|0:rb>>4
}
return u
}
This saves us 10-30% depending on platform. Not bad. But the next big step gets rid of the toString function calls altogether with an optimization classic - the look-up table. A simple 16-element lookup table will perform the job of toString(16) in much less time:
function e3() {
var h='0123456789abcdef';
var k='xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx';
/* same as e4() below */
}
function e4() {
var h=['0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'];
var k=['x','x','x','x','x','x','x','x','-','x','x','x','x','-','4','x','x','x','-','y','x','x','x','-','x','x','x','x','x','x','x','x','x','x','x','x'];
var u='',i=0,rb=Math.random()*0xffffffff|0;
while(i++<36) {
var c=k[i-1],r=rb&0xf,v=c=='x'?r:(r&0x3|0x8);
u+=(c=='-'||c=='4')?c:h[v];rb=i%8==0?Math.random()*0xffffffff|0:rb>>4
}
return u
}
The next optimization is another classic. Since we're only handling 4-bits of output in each loop iteration, let's cut the number of loops in half and process 8-bits each iteration. This is tricky since we still have to handle the RFC compliant bit positions, but it's not too hard. We then have to make a larger lookup table (16x16, or 256) to store 0x00 - 0xff, and we build it only once, outside the e5() function.
var lut = []; for (var i=0; i<256; i++) { lut[i] = (i<16?'0':'')+(i).toString(16); }
function e5() {
var k=['x','x','x','x','-','x','x','-','4','x','-','y','x','-','x','x','x','x','x','x'];
var u='',i=0,rb=Math.random()*0xffffffff|0;
while(i++<20) {
var c=k[i-1],r=rb&0xff,v=c=='x'?r:(c=='y'?(r&0x3f|0x80):(r&0xf|0x40));
u+=(c=='-')?c:lut[v];rb=i%4==0?Math.random()*0xffffffff|0:rb>>8
}
return u
}
I tried an e6() that processes 16-bits at a time, still using the 256-element LUT, and it showed the diminishing returns of optimization. Though it had fewer iterations, the inner logic was complicated by the increased processing, and it performed the same on desktop, and only ~10% faster on mobile.
The final optimization technique to apply - unroll the loop. Since we're looping a fixed number of times, we can technically write this all out by hand. I tried this once with a single random variable r that I kept re-assigning, and performance tanked. But with four variables assigned random data up front, then using the lookup table, and applying the proper RFC bits, this version smokes them all:
var lut = []; for (var i=0; i<256; i++) { lut[i] = (i<16?'0':'')+(i).toString(16); }
function e7()
{
var d0 = Math.random()*0xffffffff|0;
var d1 = Math.random()*0xffffffff|0;
var d2 = Math.random()*0xffffffff|0;
var d3 = Math.random()*0xffffffff|0;
return lut[d0&0xff]+lut[d0>>8&0xff]+lut[d0>>16&0xff]+lut[d0>>24&0xff]+'-'+
lut[d1&0xff]+lut[d1>>8&0xff]+'-'+lut[d1>>16&0x0f|0x40]+lut[d1>>24&0xff]+'-'+
lut[d2&0x3f|0x80]+lut[d2>>8&0xff]+'-'+lut[d2>>16&0xff]+lut[d2>>24&0xff]+
lut[d3&0xff]+lut[d3>>8&0xff]+lut[d3>>16&0xff]+lut[d3>>24&0xff];
}
Modualized: http://jcward.com/UUID.js - UUID.generate()
The funny thing is, generating 16 bytes of random data is the easy part. The whole trick is expressing it in String format with RFC compliance, and it's most tightly accomplished with 16 bytes of random data, an unrolled loop and lookup table.
I hope my logic is correct -- it's very easy to make a mistake in this kind of tedious bit-work. But the outputs look good to me. I hope you enjoyed this mad ride through code optimization!
Be advised: my primary goal was to show and teach potential optimization strategies. Other answers cover important topics such as collisions and truly random numbers, which are important for generating good UUIDs.
Here's some code based on RFC 4122, section 4.4 (Algorithms for Creating a UUID from Truly Random or Pseudo-Random Number).
function createUUID() {
// http://www.ietf.org/rfc/rfc4122.txt
var s = [];
var hexDigits = "0123456789abcdef";
for (var i = 0; i < 36; i++) {
s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
}
s[14] = "4"; // bits 12-15 of the time_hi_and_version field to 0010
s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1); // bits 6-7 of the clock_seq_hi_and_reserved to 01
s[8] = s[13] = s[18] = s[23] = "-";
var uuid = s.join("");
return uuid;
}
var uniqueId = Math.random().toString(36).substring(2) + (new Date()).getTime().toString(36);
If ID's are generated more than 1 millisecond apart, they are 100% unique.
If two ID's are generated at shorter intervals, and assuming that the random method is truly random, this would generate ID's that are 99.99999999999999% likely to be globally unique (collision in 1 of 10^15)
You can increase this number by adding more digits, but to generate 100% unique ID's you will need to use a global counter.
if you really do need RFC compliance, this formatting will pass as a valid version 4 GUID:
const uid = (new Date()).getTime().toString(16) + Math.random().toString(16).substring(2) + "0".repeat(16);
const guid = uid.substr(0,8) + '-' + uid.substr(8,4) + '-4000-8' + uid.substr(12,3) + '-' + uid.substr(15,12);
var u = (new Date()).getTime().toString(16) +
Math.random().toString(16).substring(2) + "0".repeat(16);
var guid = u.substr(0,8) + '-' + u.substr(8,4) + '-4000-8' +
u.substr(12,3) + '-' + u.substr(15,12);
document.getElementById("unique").innerHTML = guid;<div id="unique">
</div>Edit: The above code follow the intension, but not the letter of the RFC. Among other discrepancies it's a few random digits short. (Add more random digits if you need it) The upside is that this is really fast, compared to 100% compliant code. You can test your GUID here
Fastest GUID like string generator method in the format XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX. This does not generate standard-compliant GUID.
Ten million executions of this implementation take just 32.5 seconds, which is the fastest I've ever seen in a browser (the only solution without loops/iterations).
The function is as simple as:
/**
* Generates a GUID string.
* @returns {String} The generated GUID.
* @example af8a8416-6e18-a307-bd9c-f2c947bbb3aa
* @author Slavik Meltser (slavik@meltser.info).
* @link http://slavik.meltser.info/?p=142
*/
function guid() {
function _p8(s) {
var p = (Math.random().toString(16)+"000000000").substr(2,8);
return s ? "-" + p.substr(0,4) + "-" + p.substr(4,4) : p ;
}
return _p8() + _p8(true) + _p8(true) + _p8();
}
To test the performance, you can run this code:
console.time('t');
for (var i = 0; i < 10000000; i++) {
guid();
};
console.timeEnd('t');
I'm sure most of you will understand what I did there, but maybe there is at least one person that will need an explanation:
The algorithm:
- The
Math.random()function returns a decimal number between 0 and 1 with 16 digits after the decimal fraction point (for example0.4363923368509859). - Then we take this number and convert
it to a string with base 16 (from the example above we'll get
0.6fb7687f).
Math.random().toString(16). - Then we cut off the
0.prefix (0.6fb7687f=>6fb7687f) and get a string with eight hexadecimal characters long.
(Math.random().toString(16).substr(2,8). - Sometimes the
Math.random()function will return shorter number (for example0.4363), due to zeros at the end (from the example above, actually the number is0.4363000000000000). That's why I'm appending to this string"000000000"(a string with nine zeros) and then cutting it off withsubstr()function to make it nine characters exactly (filling zeros to the right). - The reason for adding exactly nine zeros is because of the worse case scenario, which is when the
Math.random()function will return exactly 0 or 1 (probability of 1/10^16 for each one of them). That's why we needed to add nine zeros to it ("0"+"000000000"or"1"+"000000000"), and then cutting it off from the second index (3rd character) with a length of eight characters. For the rest of the cases, the addition of zeros will not harm the result because it is cutting it off anyway.
Math.random().toString(16)+"000000000").substr(2,8).
The assembly:
- The GUID is in the following format
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX. - I divided the GUID into 4 pieces, each piece divided into 2 types (or formats):
XXXXXXXXand-XXXX-XXXX. - Now I'm building the GUID using these 2 types to assemble the GUID with call 4 pieces, as follows:
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX. - To differ between these two types, I added a flag parameter to a pair creator function
_p8(s), thesparameter tells the function whether to add dashes or not. - Eventually we build the GUID with the following chaining:
_p8() + _p8(true) + _p8(true) + _p8(), and return it.
Enjoy! :-)
Here is a combination of the top voted answer, with a workaround for Chrome's collisions:
generateGUID = (typeof(window.crypto) != 'undefined' &&
typeof(window.crypto.getRandomValues) != 'undefined') ?
function() {
// If we have a cryptographically secure PRNG, use that
// https://stackoverflow.com/questions/6906916/collisions-when-generating-uuids-in-javascript
var buf = new Uint16Array(8);
window.crypto.getRandomValues(buf);
var S4 = function(num) {
var ret = num.toString(16);
while(ret.length < 4){
ret = "0"+ret;
}
return ret;
};
return (S4(buf[0])+S4(buf[1])+"-"+S4(buf[2])+"-"+S4(buf[3])+"-"+S4(buf[4])+"-"+S4(buf[5])+S4(buf[6])+S4(buf[7]));
}
:
function() {
// Otherwise, just use Math.random
// https://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript/2117523#2117523
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);
return v.toString(16);
});
};
On jsbin if you want to test it.
Here is a totally non-compliant but very performant implementation to generate an ASCII-safe GUID-like unique identifier.
function generateQuickGuid() {
return Math.random().toString(36).substring(2, 15) +
Math.random().toString(36).substring(2, 15);
}
Generates 26 [a-z0-9] characters, yielding a UID that is both shorter and more unique than RFC compliant GUIDs. Dashes can be trivially added if human-readability matters.
Here are usage examples and timings for this function and several of this question's other answers. The timing was performed under Chrome m25, 10 million iterations each.
>>> generateQuickGuid()
"nvcjf1hs7tf8yyk4lmlijqkuo9"
"yq6gipxqta4kui8z05tgh9qeel"
"36dh5sec7zdj90sk2rx7pjswi2"
runtime: 32.5s
>>> GUID() // John Millikin
"7a342ca2-e79f-528e-6302-8f901b0b6888"
runtime: 57.8s
>>> regexGuid() // broofa
"396e0c46-09e4-4b19-97db-bd423774a4b3"
runtime: 91.2s
>>> createUUID() // Kevin Hakanson
"403aa1ab-9f70-44ec-bc08-5d5ac56bd8a5"
runtime: 65.9s
>>> UUIDv4() // Jed Schmidt
"f4d7d31f-fa83-431a-b30c-3e6cc37cc6ee"
runtime: 282.4s
>>> Math.uuid() // broofa
"5BD52F55-E68F-40FC-93C2-90EE069CE545"
runtime: 225.8s
>>> Math.uuidFast() // broofa
"6CB97A68-23A2-473E-B75B-11263781BBE6"
runtime: 92.0s
>>> Math.uuidCompact() // broofa
"3d7b7a06-0a67-4b67-825c-e5c43ff8c1e8"
runtime: 229.0s
>>> bitwiseGUID() // jablko
"baeaa2f-7587-4ff1-af23-eeab3e92"
runtime: 79.6s
>>>> betterWayGUID() // Andrea Turri
"383585b0-9753-498d-99c3-416582e9662c"
runtime: 60.0s
>>>> UUID() // John Fowler
"855f997b-4369-4cdb-b7c9-7142ceaf39e8"
runtime: 62.2s
Here is the timing code.
var r;
console.time('t');
for (var i = 0; i < 10000000; i++) {
r = FuncToTest();
};
console.timeEnd('t');
Here's a solution dated Oct. 9, 2011 from a comment by user jed at https://gist.github.com/982883:
UUIDv4 = function b(a){return a?(a^Math.random()*16>>a/4).toString(16):([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g,b)}
This accomplishes the same goal as the current highest-rated answer, but in 50+ fewer bytes by exploiting coercion, recursion, and exponential notation. For those curious how it works, here's the annotated form of an older version of the function:
UUIDv4 =
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
)
}
From sagi shkedy's technical blog:
function generateGuid() {
var result, i, j;
result = '';
for(j=0; j<32; j++) {
if( j == 8 || j == 12 || j == 16 || j == 20)
result = result + '-';
i = Math.floor(Math.random()*16).toString(16).toUpperCase();
result = result + i;
}
return result;
}
There are other methods that involve using an ActiveX control, but stay away from these!
Edit : I thought it was worth pointing out that no GUID generator can guarantee unique keys (check the wikipedia article). There is always a chance of collisions. A GUID simply offers a large enough universe of keys to reduce the change of collisions to almost nil.
You can use node-uuid (https://github.com/kelektiv/node-uuid)
Simple, fast generation of RFC4122 UUIDS.
Features:
- Generate RFC4122 version 1 or version 4 UUIDs
- Runs in node.js and browsers.
- Cryptographically strong random # generation on supporting platforms.
- Small footprint (Want something smaller? Check this out!)
Install Using NPM:
npm install uuid
Or Using uuid via browser:
Download Raw File (uuid v1): https://raw.githubusercontent.com/kelektiv/node-uuid/master/v1.js Download Raw File (uuid v4): https://raw.githubusercontent.com/kelektiv/node-uuid/master/v4.js
Want even smaller? Check this out: https://gist.github.com/jed/982883
Usage:
// Generate a v1 UUID (time-based)
const uuidV1 = require('uuid/v1');
uuidV1(); // -> '6c84fb90-12c4-11e1-840d-7b25c5ee775a'
// Generate a v4 UUID (random)
const uuidV4 = require('uuid/v4');
uuidV4(); // -> '110ec58a-a0f2-4ac4-8393-c866d813b8d1'
// Generate a v5 UUID (namespace)
const uuidV5 = require('uuid/v5');
// ... using predefined DNS namespace (for domain names)
uuidV5('hello.example.com', v5.DNS)); // -> 'fdda765f-fc57-5604-a269-52a7df8164ec'
// ... using predefined URL namespace (for, well, URLs)
uuidV5('http://example.com/hello', v5.URL); // -> '3bbcee75-cecc-5b56-8031-b6641c1ed1f1'
// ... using a custom namespace
const MY_NAMESPACE = '(previously generated unique uuid string)';
uuidV5('hello', MY_NAMESPACE); // -> '90123e1c-7512-523e-bb28-76fab9f2f73d'
ES6:
import uuid from 'uuid/v4';
const id = uuid();
A web service would be useful.
Quick Google found: http://www.hoskinson.net/GuidGenerator/
Can't vouch for this implementation, but SOMEONE must publish a bonafide GUID generator.
With such a web service, you could develop a REST web interface that consumes the GUID web service, and serves it through AJAX to javascript in a browser.
var uuid = function() {
var buf = new Uint32Array(4);
window.crypto.getRandomValues(buf);
var idx = -1;
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
idx++;
var r = (buf[idx>>3] >> ((idx%8)*4))&15;
var v = c == 'x' ? r : (r&0x3|0x8);
return v.toString(16);
});
};
EDIT:
Revisited my project that was using this function and disliked the verbosity. - But needed proper randomness.
A version based on Briguy37's answer and some bitwise operators to extract nibble sized windows from the buffer.
Should adhere to the RFC Type 4 (random) schema, since I had Problems last time parsing non-compliant uuids with Java's UUID.
Simple JavaScript module as a combination of best answers in this thread.
var crypto = window.crypto || window.msCrypto || null; // IE11 fix
var Guid = Guid || (function() {
var EMPTY = '00000000-0000-0000-0000-000000000000';
var _padLeft = function(paddingString, width, replacementChar) {
return paddingString.length >= width ? paddingString : _padLeft(replacementChar + paddingString, width, replacementChar || ' ');
};
var _s4 = function(number) {
var hexadecimalResult = number.toString(16);
return _padLeft(hexadecimalResult, 4, '0');
};
var _cryptoGuid = function() {
var buffer = new window.Uint16Array(8);
window.crypto.getRandomValues(buffer);
return [_s4(buffer[0]) + _s4(buffer[1]), _s4(buffer[2]), _s4(buffer[3]), _s4(buffer[4]), _s4(buffer[5]) + _s4(buffer[6]) + _s4(buffer[7])].join('-');
};
var _guid = function() {
var currentDateMilliseconds = new Date().getTime();
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(currentChar) {
var randomChar = (currentDateMilliseconds + Math.random() * 16) % 16 | 0;
currentDateMilliseconds = Math.floor(currentDateMilliseconds / 16);
return (currentChar === 'x' ? randomChar : (randomChar & 0x7 | 0x8)).toString(16);
});
};
var create = function() {
var hasCrypto = crypto != 'undefined' && crypto !== null,
hasRandomValues = typeof(window.crypto.getRandomValues) != 'undefined';
return (hasCrypto && hasRandomValues) ? _cryptoGuid() : _guid();
};
return {
newGuid: create,
empty: EMPTY
};
})();
// DEMO: Create and show GUID
console.log(Guid.newGuid());Usage:
Guid.newGuid()
"c6c2d12f-d76b-5739-e551-07e6de5b0807"
Guid.empty
"00000000-0000-0000-0000-000000000000"
From good ol' wikipedia there's a link to a javascript implementation of UUID.
It looks fairly elegant, and could perhaps be improved by salting with a hash of the client's IP address. This hash could perhaps be inserted into the html document server-side for use by the client-side javascript.
UPDATE : The original site has had a shuffle, here is the updated version
Well, this has a bunch of answers already, but unfortunately there's not a "true" random in the bunch. The version below is an adaptation of broofa's answer, but updated to include a "true" random function that uses crypto libraries where available, and the Alea() function as a fallback.
Math.log2 = Math.log2 || function(n){ return Math.log(n) / Math.log(2); }
Math.trueRandom = (function() {
var crypt = window.crypto || window.msCrypto;
if (crypt && crypt.getRandomValues) {
// if we have a crypto library, use it
var random = function(min, max) {
var rval = 0;
var range = max - min;
if (range < 2) {
return min;
}
var bits_needed = Math.ceil(Math.log2(range));
if (bits_needed > 53) {
throw new Exception("We cannot generate numbers larger than 53 bits.");
}
var bytes_needed = Math.ceil(bits_needed / 8);
var mask = Math.pow(2, bits_needed) - 1;
// 7776 -> (2^13 = 8192) -1 == 8191 or 0x00001111 11111111
// Create byte array and fill with N random numbers
var byteArray = new Uint8Array(bytes_needed);
crypt.getRandomValues(byteArray);
var p = (bytes_needed - 1) * 8;
for(var i = 0; i < bytes_needed; i++ ) {
rval += byteArray[i] * Math.pow(2, p);
p -= 8;
}
// Use & to apply the mask and reduce the number of recursive lookups
rval = rval & mask;
if (rval >= range) {
// Integer out of acceptable range
return random(min, max);
}
// Return an integer that falls within the range
return min + rval;
}
return function() {
var r = random(0, 1000000000) / 1000000000;
return r;
};
} else {
// From http://baagoe.com/en/RandomMusings/javascript/
// Johannes Baagøe <baagoe@baagoe.com>, 2010
function Mash() {
var n = 0xefc8249d;
var mash = function(data) {
data = data.toString();
for (var i = 0; i < data.length; i++) {
n += data.charCodeAt(i);
var h = 0.02519603282416938 * n;
n = h >>> 0;
h -= n;
h *= n;
n = h >>> 0;
h -= n;
n += h * 0x100000000; // 2^32
}
return (n >>> 0) * 2.3283064365386963e-10; // 2^-32
};
mash.version = 'Mash 0.9';
return mash;
}
// From http://baagoe.com/en/RandomMusings/javascript/
function Alea() {
return (function(args) {
// Johannes Baagøe <baagoe@baagoe.com>, 2010
var s0 = 0;
var s1 = 0;
var s2 = 0;
var c = 1;
if (args.length == 0) {
args = [+new Date()];
}
var mash = Mash();
s0 = mash(' ');
s1 = mash(' ');
s2 = mash(' ');
for (var i = 0; i < args.length; i++) {
s0 -= mash(args[i]);
if (s0 < 0) {
s0 += 1;
}
s1 -= mash(args[i]);
if (s1 < 0) {
s1 += 1;
}
s2 -= mash(args[i]);
if (s2 < 0) {
s2 += 1;
}
}
mash = null;
var random = function() {
var t = 2091639 * s0 + c * 2.3283064365386963e-10; // 2^-32
s0 = s1;
s1 = s2;
return s2 = t - (c = t | 0);
};
random.uint32 = function() {
return random() * 0x100000000; // 2^32
};
random.fract53 = function() {
return random() +
(random() * 0x200000 | 0) * 1.1102230246251565e-16; // 2^-53
};
random.version = 'Alea 0.9';
random.args = args;
return random;
}(Array.prototype.slice.call(arguments)));
};
return Alea();
}
}());
Math.guid = function() {
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
var r = Math.trueRandom() * 16 | 0,
v = c == 'x' ? r : (r & 0x3 | 0x8);
return v.toString(16);
});
};
This create version 4 UUID (created from pseudo random numbers) :
function uuid()
{
var chars = '0123456789abcdef'.split('');
var uuid = [], rnd = Math.random, r;
uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
uuid[14] = '4'; // version 4
for (var i = 0; i < 36; i++)
{
if (!uuid[i])
{
r = 0 | rnd()*16;
uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r & 0xf];
}
}
return uuid.join('');
}
Here is a sample of the UUIDs generated :
682db637-0f31-4847-9cdf-25ba9613a75c
97d19478-3ab2-4aa1-b8cc-a1c3540f54aa
2eed04c9-2692-456d-a0fd-51012f947136
JavaScript project on GitHub - https://github.com/LiosK/UUID.js
UUID.js The RFC-compliant UUID generator for JavaScript.
See RFC 4122 http://www.ietf.org/rfc/rfc4122.txt.
Features Generates RFC 4122 compliant UUIDs.
Version 4 UUIDs (UUIDs from random numbers) and version 1 UUIDs (time-based UUIDs) are available.
UUID object allows a variety of access to the UUID including access to the UUID fields.
Low timestamp resolution of JavaScript is compensated by random numbers.
// RFC 4122
//
// A UUID is 128 bits long
//
// String representation is five fields of 4, 2, 2, 2, and 6 bytes.
// Fields represented as lowercase, zero-filled, hexadecimal strings, and
// are separated by dash characters
//
// A version 4 UUID is generated by setting all but six bits to randomly
// chosen values
var uuid = [
Math.random().toString(16).slice(2, 10),
Math.random().toString(16).slice(2, 6),
// Set the four most significant bits (bits 12 through 15) of the
// time_hi_and_version field to the 4-bit version number from Section
// 4.1.3
(Math.random() * .0625 /* 0x.1 */ + .25 /* 0x.4 */).toString(16).slice(2, 6),
// Set the two most significant bits (bits 6 and 7) of the
// clock_seq_hi_and_reserved to zero and one, respectively
(Math.random() * .25 /* 0x.4 */ + .5 /* 0x.8 */).toString(16).slice(2, 6),
Math.random().toString(16).slice(2, 14)].join('-');
Adjusted my own UUID/GUID generator with some extras here.
I'm using the following Kybos random number generator to be a bit more cryptographically sound.
Below is my script with the Mash and Kybos methods from baagoe.com excluded.
//UUID/Guid Generator
// use: UUID.create() or UUID.createSequential()
// convenience: UUID.empty, UUID.tryParse(string)
(function(w){
// From http://baagoe.com/en/RandomMusings/javascript/
// Johannes Baagøe <baagoe@baagoe.com>, 2010
//function Mash() {...};
// From http://baagoe.com/en/RandomMusings/javascript/
//function Kybos() {...};
var rnd = Kybos();
//UUID/GUID Implementation from http://frugalcoder.us/post/2012/01/13/javascript-guid-uuid-generator.aspx
var UUID = {
"empty": "00000000-0000-0000-0000-000000000000"
,"parse": function(input) {
var ret = input.toString().trim().toLowerCase().replace(/^[\s\r\n]+|[\{\}]|[\s\r\n]+$/g, "");
if ((/[a-f0-9]{8}\-[a-f0-9]{4}\-[a-f0-9]{4}\-[a-f0-9]{4}\-[a-f0-9]{12}/).test(ret))
return ret;
else
throw new Error("Unable to parse UUID");
}
,"createSequential": function() {
var ret = new Date().valueOf().toString(16).replace("-","")
for (;ret.length < 12; ret = "0" + ret);
ret = ret.substr(ret.length-12,12); //only least significant part
for (;ret.length < 32;ret += Math.floor(rnd() * 0xffffffff).toString(16));
return [ret.substr(0,8), ret.substr(8,4), "4" + ret.substr(12,3), "89AB"[Math.floor(Math.random()*4)] + ret.substr(16,3), ret.substr(20,12)].join("-");
}
,"create": function() {
var ret = "";
for (;ret.length < 32;ret += Math.floor(rnd() * 0xffffffff).toString(16));
return [ret.substr(0,8), ret.substr(8,4), "4" + ret.substr(12,3), "89AB"[Math.floor(Math.random()*4)] + ret.substr(16,3), ret.substr(20,12)].join("-");
}
,"random": function() {
return rnd();
}
,"tryParse": function(input) {
try {
return UUID.parse(input);
} catch(ex) {
return UUID.empty;
}
}
};
UUID["new"] = UUID.create;
w.UUID = w.Guid = UUID;
}(window || this));The better way:
function(
a,b // placeholders
){
for( // loop :)
b=a=''; // b - result , a - numeric variable
a++<36; //
b+=a*51&52 // if "a" is not 9 or 14 or 19 or 24
? // return a random number or 4
(
a^15 // if "a" is not 15
? // genetate a random number from 0 to 15
8^Math.random()*
(a^20?16:4) // unless "a" is 20, in which case a random number from 8 to 11
:
4 // otherwise 4
).toString(16)
:
'-' // in other cases (if "a" is 9,14,19,24) insert "-"
);
return b
}
Minimized:
function(a,b){for(b=a='';a++<36;b+=a*51&52?(a^15?8^Math.random()*(a^20?16:4):4).toString(16):'-');return b}
I wanted to understand broofa's answer, so I expanded it and added comments:
var uuid = function () {
return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(
/[xy]/g,
function (match) {
/*
* Create a random nibble. The two clever bits of this code:
*
* - Bitwise operations will truncate floating point numbers
* - For a bitwise OR of any x, x | 0 = x
*
* So:
*
* Math.random * 16
*
* creates a random floating point number
* between 0 (inclusive) and 16 (exclusive) and
*
* | 0
*
* truncates the floating point number into an integer.
*/
var randomNibble = Math.random() * 16 | 0;
/*
* Resolves the variant field. If the variant field (delineated
* as y in the initial string) is matched, the nibble must
* match the mask (where x is a do-not-care bit):
*
* 10xx
*
* This is achieved by performing the following operations in
* sequence (where x is an intermediate result):
*
* - x & 0x3, which is equivalent to x % 3
* - x | 0x8, which is equivalent to x + 8
*
* This results in a nibble between 8 inclusive and 11 exclusive,
* (or 1000 and 1011 in binary), all of which satisfy the variant
* field mask above.
*/
var nibble = (match == 'y') ?
(randomNibble & 0x3 | 0x8) :
randomNibble;
/*
* Ensure the nibble integer is encoded as base 16 (hexadecimal).
*/
return nibble.toString(16);
}
);
};
ES6 sample
const guid=()=> {
const s4=()=> Math.floor((1 + Math.random()) * 0x10000).toString(16).substring(1);
return `${s4() + s4()}-${s4()}-${s4()}-${s4()}-${s4() + s4() + s4()}`;
}
It's just a simple AJAX call...
If anyone is still interested, here's my solution.
On the server side:
[WebMethod()]
public static string GenerateGuid()
{
return Guid.NewGuid().ToString();
}
On the client side:
var myNewGuid = null;
PageMethods.GenerateGuid(
function(result, userContext, methodName)
{
myNewGuid = result;
},
function()
{
alert("WebService call failed.");
}
);
For those wanting an rfc4122 version 4 compliant solution with speed considerations (few calls to Math.random()):
function UUID() {
var nbr, randStr = "";
do {
randStr += (nbr = Math.random()).toString(16).substr(2);
} while (randStr.length < 30);
return [
randStr.substr(0, 8), "-",
randStr.substr(8, 4), "-4",
randStr.substr(12, 3), "-",
((nbr*4|0)+8).toString(16), // [89ab]
randStr.substr(15, 3), "-",
randStr.substr(18, 12)
].join("");
}
The above function should have a decent balance between speed and randomness.
This one is based on date, and add a random suffix to "ensure" uniqueness. Works well for css identifiers. It always returns something like and is easy to hack:
uid-139410573297741
var getUniqueId = function (prefix) {
var d = new Date().getTime();
d += (parseInt(Math.random() * 100)).toString();
if (undefined === prefix) {
prefix = 'uid-';
}
d = prefix + d;
return d;
};
I know, it is an old question. Just for completeness, if your environment is SharePoint, there is a utility function called SP.Guid.newGuid (msdn link) which creates a new guid. This function is inside the sp.init.js file. If you rewrite this function (to remove some other dependencies from other private functions), it looks like this:
var newGuid = function () {
var result = '';
var hexcodes = "0123456789abcdef".split("");
for (var index = 0; index < 32; index++) {
var value = Math.floor(Math.random() * 16);
switch (index) {
case 8:
result += '-';
break;
case 12:
value = 4;
result += '-';
break;
case 16:
value = value & 3 | 8;
result += '-';
break;
case 20:
result += '-';
break;
}
result += hexcodes[value];
}
return result;
};
There is a jQuery plugin that handles Guid's nicely @ http://plugins.jquery.com/project/GUID_Helper
jQuery.Guid.Value()
Returns value of internal Guid. If no guid has been specified, returns a new one (value is then stored internally).
jQuery.Guid.New()
Returns a new Guid and sets it's value internally.
jQuery.Guid.Empty()
Returns an empty Guid 00000000-0000-0000-0000-000000000000.
jQuery.Guid.IsEmpty()
Returns boolean. True if empty/undefined/blank/null.
jQuery.Guid.IsValid()
Returns boolean. True valid guid, false if not.
jQuery.Guid.Set()
Retrns Guid. Sets Guid to user specified Guid, if invalid, returns an empty guid.
Simple code that uses crypto.getRandomValues(a) on supported browsers (IE11+, iOS7+, FF21+, Chrome, Android Chrome). Avoids using Math.random() because that can cause collisions (for example 20 collisions for 4000 generated uuids in a real situation by Muxa).
function uuid() {
function randomDigit() {
if (crypto && crypto.getRandomValues) {
var rands = new Uint8Array(1);
crypto.getRandomValues(rands);
return (rands[0] % 16).toString(16);
} else {
return ((Math.random() * 16) | 0).toString(16);
}
}
var crypto = window.crypto || window.msCrypto;
return 'xxxxxxxx-xxxx-4xxx-8xxx-xxxxxxxxxxxx'.replace(/x/g, randomDigit);
}
Notes:
- Optimised for code readability not speed, so suitable for say a few hundred uuid's per second. Generates about 10000 uuid() per second in Chromium on my laptop using http://jsbin.com/fuwigo/1 to measure performance.
- Only uses 8 for "y" because that simplifies code readability (y is allowed to be 8, 9, A or B).
