Create a unique number with javascript time

Question

I need to generate unique id numbers on the fly using javascript. In the past, I've done this by creating a number using time. The number would be made up of the four digit year, two digit month, two digit day, two digit hour, two digit minute, two digit second, and three digit millisecond. So it would look something like this: 20111104103912732 ... this would give enough certainty of a unique number for my purposes.

It's been a while since I've done this and I don't have the code anymore. Anyone have the code to do this, or have a better suggestion for generating a unique ID?

Answer 1

A better approach would be:

new Date().valueOf();

instead of

new Date().getUTCMilliseconds();

valueOf() is "most likely" a unique number. http://www.w3schools.com/jsref/jsref_valueof_date.asp.

Answer 2

The shortest way to create a number that you can be pretty sure will be unique among as many separate instances as you can think of is

Date.now() + Math.random()

If there is a 1 millisecond difference in function call, it is 100% guaranteed to generate a different number. For function calls within the same millisecond you should only start to be worried if you are creating more than a few million numbers within this same millisecond, which is not very probable.

For more on the probability of getting a repeated number within the same millisecond see https://stackoverflow.com/a/28220928/4617597

Answer 3

If you just want a unique-ish number, then

var timestamp = new Date().getUTCMilliseconds();

would get you a simple number. But if you need the readable version, you're in for a bit of processing:

var now = new Date();

timestamp = now.getFullYear().toString(); // 2011
timestamp += (now.getMonth < 9 ? '0' : '') + now.getMonth().toString(); // JS months are 0-based, so +1 and pad with 0's
timestamp += ((now.getDate < 10) ? '0' : '') + now.getDate().toString(); // pad with a 0
... etc... with .getHours(), getMinutes(), getSeconds(), getMilliseconds()

Answer 4

Here's what I do when I want something smaller than a bunch of numbers - change base.

var uid = (new Date().getTime()).toString(36)

Answer 5

This performs faster than creating a Date instance, uses less code and will always produce a unique number (locally):

function uniqueNumber() {
    var date = Date.now();

    // If created at same millisecond as previous
    if (date <= uniqueNumber.previous) {
        date = ++uniqueNumber.previous;
    } else {
        uniqueNumber.previous = date;
    }

    return date;
}

uniqueNumber.previous = 0;

jsfiddle: http://jsfiddle.net/j8aLocan/

I've released this on Bower and npm: https://github.com/stevenvachon/unique-number

You could also use something more elaborate such as cuid, puid or shortid to generate a non-number.

Answer 6

I use

Math.floor(new Date().valueOf() * Math.random())

So if by any chance the code is fired at the same time there is also a teeny chance that the random numbers will be the same.

Answer 7

In 2023, you can use the in-browser Crypto API to generate cryptographically strong random values.

function getRandomNumbers() {
  const typedArray = new Uint8Array(10);
  const randomValues = window.crypto.getRandomValues(typedArray);
  return randomValues.join('');
}

console.log(getRandomNumbers());
// 1857488137147725264738

function getRandomNumbers() {
  const typedArray = new Uint8Array(10);
  const randomValues = window.crypto.getRandomValues(typedArray);
  return randomValues.join('');
}

console.log(getRandomNumbers());

both Uint8Array constructor and Crypto.getRandomValues are supported on all major browsers, including IE11

Answer 8

This should do :

var uniqueNumber = new Date().getTime(); // milliseconds since 1st Jan. 1970

Answer 9

if you want a unique number after few mili seconds then use Date.now(), if you want to use it inside a for loop then use Date.now() and Math.random() together

unique number inside a for loop

function getUniqueID(){
    for(var i = 0; i< 5; i++)
      console.log(Date.now() + ( (Math.random()*100000).toFixed()))
}
getUniqueID()

output:: all numbers are unique

15598251485988384 155982514859810330 155982514859860737 155982514859882244 155982514859883316

unique number without Math.random()

function getUniqueID(){
        for(var i = 0; i< 5; i++)
          console.log(Date.now())
    }
    getUniqueID()

output:: Numbers are repeated

1559825328327 1559825328327 1559825328327 1559825328328 1559825328328

Answer 10

From investigating online I came up with the following object that creates a unique id per session:

        window.mwUnique ={
        prevTimeId : 0,
        prevUniqueId : 0,
        getUniqueID : function(){
            try {
                var d=new Date();
                var newUniqueId = d.getTime();
                if (newUniqueId == mwUnique.prevTimeId)
                    mwUnique.prevUniqueId = mwUnique.prevUniqueId + 1;
                else {
                    mwUnique.prevTimeId = newUniqueId;
                    mwUnique.prevUniqueId = 0;
                }
                newUniqueId = newUniqueId + '' + mwUnique.prevUniqueId;
                return newUniqueId;                     
            }
            catch(e) {
                mwTool.logError('mwUnique.getUniqueID error:' + e.message + '.');
            }
        }            
    }

It maybe helpful to some people.

Cheers

Andrew

Answer 11

This also should do:

(function() {
    var uniquePrevious = 0;
    uniqueId = function() {
        return uniquePrevious++;
    };
}());

Answer 12

In ES6:

const ID_LENGTH = 36
const START_LETTERS_ASCII = 97 // Use 64 for uppercase
const ALPHABET_LENGTH = 26

const uniqueID = () => [...new Array(ID_LENGTH)]
  .map(() => String.fromCharCode(START_LETTERS_ASCII + Math.random() * ALPHABET_LENGTH))
 .join('')

Example:

 > uniqueID()
 > "bxppcnanpuxzpyewttifptbklkurvvetigra"

Answer 13

Always get unique Id in JS

function getUniqueId(){
   return (new Date().getTime()).toString(36) + new Date().getUTCMilliseconds();
}

getUniqueId()    // Call the function

------------results like

//"ka2high4264"

//"ka2hj115905"

//"ka2hj1my690"

//"ka2hj23j287"

//"ka2hj2jp869"

Answer 14

Updated for 2021, numbers and ids are not guaranteed to be unique but should be satisfactory unique enough:

(oh, and who knew something.toString(36) is even a thing )

// a pseudo-random floating number based on Date.now()
const generateRandomNumber = () =>
  Math.log2(Date.now()) + Math.random();

console.log("a pseudo-random floating number based on Date.now():");
console.log(generateRandomNumber());

// a locally unique-ish HTML id
const generateUniqueId = () => `_${Date.now().toString(36)}${Math.floor(Number.MAX_SAFE_INTEGER * Math.random()).toString(36)}`;

console.log("a locally unique-ish HTML id:");
console.log(generateUniqueId())

// a pseudo-random BigInt
const generateRandomBigInt = () =>
  BigInt(Date.now()) * BigInt(Number.MAX_SAFE_INTEGER) +
  BigInt(Math.floor(Number.MAX_SAFE_INTEGER * Math.random()));

console.log("a pseudo-random BigInt:");
console.log(generateRandomBigInt().toString());

// same but base32-encoded (each char is 5 bits)

console.log("same but base32-encoded (each char is 5 bits):");
console.log(generateRandomBigInt().toString(32));

// extracting the "Date.now" timestamp of when it was generated:

console.log('extracting the "Date.now" timestamp of when it was generated:');
console.log(Number(generateRandomBigInt() / BigInt(Number.MAX_SAFE_INTEGER)))

// generate a run of random BigInt in ascending order

function generateRandomBigIntFactory() {
  let count = 0, prev = 0;
  return () => {
    const now = Date.now();
    if (now === prev) { ++count; }
    else { count = 0; prev = now; }
    return (BigInt(now) * BigInt(16384) + BigInt(count)) * BigInt(Number.MAX_SAFE_INTEGER) +
      BigInt(Math.floor(Math.random() * Number.MAX_SAFE_INTEGER)); 
  }    
}

// verify the order is ascending
const generate = generateRandomBigIntFactory();
let prev = 0;
for (let i = 0; i < 65536; i++) {
  const num = generate();
  if (num <= prev) console.log(`error: ${prev}, ${num}`);
  prev = num;
}

console.log("the last random BigInt:");
console.log(prev.toString());

Answer 15

use this:for creating unique number in javascript

var uniqueNumber=(new Date().getTime()).toString(36);

It really works. :)

Answer 16

simple solution I found

var today = new Date().valueOf();

console.log( today );

Answer 17

This creates an almost guaranteed unique 32 character key client side, if you want just numbers change the "chars" var.

var d = new Date().valueOf();
var n = d.toString();
var result = '';
var length = 32;
var p = 0;
var chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

for (var i = length; i > 0; --i){
    result += ((i & 1) && n.charAt(p) ? '<b>' + n.charAt(p) + '</b>' : chars[Math.floor(Math.random() * chars.length)]);
    if(i & 1) p++;
};

https://jsfiddle.net/j0evrdf1/1/

Answer 18

    function UniqueValue(d){
        var dat_e = new Date();
        var uniqu_e = ((Math.random() *1000) +"").slice(-4)

        dat_e = dat_e.toISOString().replace(/[^0-9]/g, "").replace(dat_e.getFullYear(),uniqu_e);
        if(d==dat_e)
            dat_e = UniqueValue(dat_e);
        return dat_e;
    }

Call 1: UniqueValue('0')
Call 2: UniqueValue(UniqueValue('0')) // will be complex

Sample Output:
for(var i =0;i<10;i++){ console.log(UniqueValue(UniqueValue('0')));}
60950116113248802
26780116113248803
53920116113248803
35840116113248803
47430116113248803
41680116113248803
42980116113248804
34750116113248804
20950116113248804
03730116113248804

Answer 19

Since milliseconds are not updated every millisecond in node, following is an answer. This generates a unique human readable ticket number. I am new to programming and nodejs. Please correct me if I am wrong.

function get2Digit(value) {
if (value.length == 1) return "0" + "" + value;
else return value;

}

function get3Digit(value) {
if (value.length == 1) return "00" + "" + value;
else return value;

}

function generateID() {
    var d = new Date();
    var year = d.getFullYear();
    var month = get2Digit(d.getMonth() + 1);
    var date = get2Digit(d.getDate());
    var hours = get2Digit(d.getHours());
    var minutes = get2Digit(d.getMinutes());
    var seconds = get2Digit(d.getSeconds());
    var millSeconds = get2Digit(d.getMilliseconds());
    var dateValue = year + "" + month + "" + date;
    var uniqueID = hours + "" + minutes + "" + seconds + "" + millSeconds;

    if (lastUniqueID == "false" || lastUniqueID < uniqueID) lastUniqueID = uniqueID;
    else lastUniqueID = Number(lastUniqueID) + 1;
    return dateValue + "" + lastUniqueID;
}

Answer 20

let uuid = ((new Date().getTime()).toString(36))+'_'+(Date.now() + Math.random().toString()).split('.').join("_")

sample result "k3jobnvt_15750033412250_18299601769317408"

Answer 21

I came across this question while trying to find a simple UID generation technique that was also sortable (so I can order by uid and items will appear in order of creation / uid generation). The major problem with most (all?) of the solutions here is that they either rely on millisecond accuracy (at best) == clashes(!) or a pseudo-random number == clashes(!) && non-sortable(!).

Technique below uses micro-second precision where available (i.e. not where fingerprinting-resistance techniques are in play, e.g. firefox) combined with an incrementing, stateful suffix. Not perfect, or particularly performant for large numbers of IDs (see example with 1,000,000 below), but it works and is reversible.

// return a uid, sortable by creation order
let increment;
let tuidPrev;

const uid = (uidPrev) => {
  // get current time to microsecond precision (if available) and remove decimals
  const tuid = ((performance.timing.navigationStart + performance.now()) * 1000)
    // convert timestamp to base36 string
    .toString(36);

  // previous uid has been provided (stateful)
  if (uidPrev) {
    tuidPrev = uidPrev.slice(0, 10);
    increment = uidPrev.length > 10 ? parseInt(uidPrev.slice(10), 36) : 0;
  }

  // if tuid is changed reset the increment
  if (tuid !== tuidPrev) {
    tuidPrev = tuid;
    increment = 0;
  }

  // return timed uid + suffix (4^36 values) === very unique id!
  return tuid + ('000' + (increment++).toString(36)).slice(-4);
}


// EXAMPLE (check the console!)
const iterations = 1000000;
const uids = [];
const uidMap = {};
const timeMap = {}
const microMap = {};
let time = performance.now();
for (let i = 0; i < iterations; i++) {
  const id = uid();
  uids.push(id);
  uidMap[id] = i;
  timeMap[Date.now()] = i;
  microMap[performance.now()] = i;
}

console.log(`Time taken: ${performance.now() - time}ms`);
console.log('Unique IDs:', Object.keys(uidMap).length.toLocaleString());
console.log('Clashing timestamps:', (iterations - Object.keys(timeMap).length).toLocaleString());
console.log('Clashing microseconds:', (iterations - Object.keys(microMap).length).toLocaleString());
console.log('Sortable:', !uids.slice().sort().find((id, i) => uids[i] !== id))

Answer 22

The usual way in which I generate unique IDs is by using Date.now();

const ID = Date.now();
console.log(ID);

The other way is by using a library as idgp which can be installed using npm.

The link: https://www.npmjs.com/package/idgp

Answer 23

try this

    function generateId() {
    return +new Date();
}

and then assign to variable

const uniqueId = generateId();

Answer 24

Assumed that the solution proposed by @abarber it's a good solution because uses (new Date()).getTime() so it has a windows of milliseconds and sum a tick in case of collisions in this interval, we could consider to use built-in as we can clearly see here in action:

Fist we can see here how there can be collisions in the 1/1000 window frame using (new Date()).getTime():

console.log( (new Date()).getTime() ); console.log( (new Date()).getTime() )
VM1155:1 1469615396590
VM1155:1 1469615396591
console.log( (new Date()).getTime() ); console.log( (new Date()).getTime() )
VM1156:1 1469615398845
VM1156:1 1469615398846
console.log( (new Date()).getTime() ); console.log( (new Date()).getTime() )
VM1158:1 1469615403045
VM1158:1 1469615403045

Second we try the proposed solution that avoid collisions in the 1/1000 window:

console.log( window.mwUnique.getUniqueID() ); console.log( window.mwUnique.getUniqueID() ); 
VM1159:1 14696154132130
VM1159:1 14696154132131

That said we could consider to use functions like the node process.nextTick that is called in the event loop as a single tick and it's well explained here. Of course in the browser there is no process.nextTick so we have to figure how how to do that. This implementation will install a nextTick function in the browser using the most closer functions to the I/O in the browser that are setTimeout(fnc,0), setImmediate(fnc), window.requestAnimationFrame. As suggested here we could add the window.postMessage, but I leave this to the reader since it needs a addEventListener as well. I have modified the original module versions to keep it simpler here:

getUniqueID = (c => {
 if(typeof(nextTick)=='undefined')
nextTick = (function(window, prefixes, i, p, fnc) {
    while (!fnc && i < prefixes.length) {
        fnc = window[prefixes[i++] + 'equestAnimationFrame'];
    }
    return (fnc && fnc.bind(window)) || window.setImmediate || function(fnc) {window.setTimeout(fnc, 0);};
})(window, 'r webkitR mozR msR oR'.split(' '), 0);
 nextTick(() => {
   return c( (new Date()).getTime() )  
 })
})

So we have in the 1/1000 window:

getUniqueID(function(c) { console.log(c); });getUniqueID(function(c) { console.log(c); });
undefined
VM1160:1 1469615416965
VM1160:1 1469615416966

Answer 25

Maybe even better would be to use getTime() or valueOf(), but this way it returns unique plus human understandable number (representing date and time):

window.getUniqNr = function() {
  var now = new Date(); 
  if (typeof window.uniqCounter === 'undefined') window.uniqCounter = 0; 
  window.uniqCounter++; 
  var m = now.getMonth(); var d = now.getDay(); 
  var h = now.getHours(); var i = now.getMinutes(); 
  var s = now.getSeconds(); var ms = now.getMilliseconds();
  timestamp = now.getFullYear().toString() 
  + (m <= 9 ? '0' : '') + m.toString()
  +( d <= 9 ? '0' : '') + d.toString() 
  + (h <= 9 ? '0' : '') + h.toString() 
  + (i <= 9 ? '0' : '') + i.toString() 
  + (s <= 9 ? '0' : '') + s.toString() 
  + (ms <= 9 ? '00' : (ms <= 99 ? '0' : '')) + ms.toString() 
  + window.uniqCounter; 

  return timestamp;
};
window.getUniqNr();

Answer 26

let now = new Date();
let timestamp = now.getFullYear().toString();
let month = now.getMonth() + 1;
timestamp += (month < 10 ? '0' : '') + month.toString();
timestamp += (now.getDate() < 10 ? '0' : '') + now.getDate().toString();
timestamp += (now.getHours() < 10 ? '0' : '') + now.getHours().toString();
timestamp += (now.getMinutes() < 10 ? '0' : '') + now.getMinutes().toString();
timestamp += (now.getSeconds() < 10 ? '0' : '') + now.getSeconds().toString();
timestamp += (now.getMilliseconds() < 100 ? '0' : '') + now.getMilliseconds().toString();

Answer 27

Easy and always get unique value :

const uniqueValue = (new Date()).getTime() + Math.trunc(365 * Math.random());
**OUTPUT LIKE THIS** : 1556782842762

Answer 28

I have done this way

function uniqeId() {
   var ranDom = Math.floor(new Date().valueOf() * Math.random())
   return _.uniqueId(ranDom);
}

Answer 29

function getUniqueNumber() {

    function shuffle(str) {
        var a = str.split("");
        var n = a.length;
        for(var i = n - 1; i > 0; i--) {
            var j = Math.floor(Math.random() * (i + 1));
            var tmp = a[i];
            a[i] = a[j];
            a[j] = tmp;
        }
        return a.join("");
    }
    var str = new Date().getTime() + (Math.random()*999 +1000).toFixed() //string
    return Number.parseInt(shuffle(str));   
}

Answer 30

in reference to #Marcelo Lazaroni solution above

Date.now() + Math.random()

returns a number such as this 1567507511939.4558 (limited to 4 decimals), and will give non-unique numbers (or collisions) every 0.1%.

adding toString() fixes this

Date.now() + Math.random().toString()

returns '15675096840820.04510962122198503' (a string), and is further so 'slow' that you never get the 'same' millisecond, anyway.

Answer 31

Generate Unique Numbers with javascript time V2.0

JavaScript time values: dates as milliseconds since 1970-01-01
100% guaranteed to generate a different number...

let Q = {};
Q.in = document.querySelector('#in');
Q.info = document.querySelector('#butStart');
Q.copy = document.querySelector('#butCopy');
Q.demo = document.querySelector('#demo');

function genUniqueNum() {
    let kol = Q.in.value,
        data, tmp, out = '';
    let i = 0;

    while (i < kol) {
        data = new Date().getTime();
        if (data != tmp) {
            out += `${data}\n`;
            tmp = data;
            i++;
        }
    }
    Q.demo.value += out;
}

function elemTarget(e) {
    e = e || window.event;
    e.preventDefault();
    return e.target;
}

document.addEventListener('click', (e) => {
    let elem = elemTarget(e);

    if (elem.id === 'butStart') {
        genUniqueNum();
    }
    if (elem.id === 'butCopy' && Q.demo.value) {
        Q.demo.select();
        Q.demo.setSelectionRange(0, 99999);
        document.execCommand("copy");
    }
    if (elem.id === 'butClear') {
        Q.demo.value = '';
    }
});

#in{
  width: 91px;
}

#butStart,
#butCopy,
#butClear {
  width: 100px;
  margin: 3px 2px 0px 0;
  height: 25px;
}

#butCopy {
  margin: 0 5px;
}

#demo {
  width: 200px;
  height: 100px;
  margin: 5px 0 0;
}

  <input type="number" id="in" maxlength="1000000" minlength="1" value="5">
  <label> - Amount</label><br>
  <button id="butStart">Start</button><br>
  <textarea id="demo"></textarea><br>
  <button id="butClear">Clear</button><button id="butCopy">Copy</button>

Fork-codepen.io

Answer 32

Using toString(36), slightly slow, here is the faster and unique solution:

new Date().getUTCMilliseconds().toString() +
"-" +
Date.now() +
"-" +
filename.replace(/\s+/g, "-").toLowerCase()

Answer 33

To get a unique number:

function getUnique(){
    return new Date().getTime().toString() + window.crypto.getRandomValues(new Uint32Array(1))[0];
}
// or 
function getUniqueNumber(){
    const now = new Date();
    return Number([
        now.getFullYear(),
        now.getMonth(),
        now.getDate(),
        now.getHours(),
        now.getMinutes(),
        now.getUTCMilliseconds(),
        window.crypto.getRandomValues(new Uint8Array(1))[0]
    ].join(""));
}

Example:

getUnique()
"15951973277543340653840"

for (let i=0; i<5; i++){
    console.log( getUnique() );
}
15951974746301197061197
15951974746301600673248
15951974746302690320798
15951974746313778184640
1595197474631922766030

getUniqueNumber()
20206201121832230

for (let i=0; i<5; i++){
    console.log( getUniqueNumber() );
}
2020620112149367
2020620112149336
20206201121493240
20206201121493150
20206201121494200

you can change the length using:

new Uint8Array(1)[0]
// or
new Uint16Array(1)[0]
// or
new Uint32Array(1)[0]

Answer 34

This returns unique value even when inside fast loop.

ofcourse this can be improved much more

const getUniqueValue = (strength = 2, int=false) => {
    
    const u = () => (Math.random() * 10000).toString().replace('.','');
    
    let r = '';
    
    for (let i=0; i < strength; i++) {
        r += u();
    }
    
    return (int) ? parseInt(r) : r;
}

[1,2,3,5,6,7,8,9,10].map(item => console.log(getUniqueValue()));

Answer 35

Adding my take on this because I wanted a solution where the UID would be:

• Likely unique
• Legible (and can be used in an URL)
• Sortable (by create date)

const uid = new Date().toISOString().replaceAll(/[-:TZ]/g, '.') + Math.random().toString().substring(2,7)
// '2022.04.15.03.56.36.197.50167'

NOTE: You can tweak the substring second parameter to increase the chances of uniqueness but you will be making the uid longer. Depends on your use case.

Answer 36

function createUniqueId() {
  var date = new Date().getTime();
  var uniqueId = "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx".replace(
    /[xy]/g,
    function (c) {
      var r = (date + Math.random() * 16) % 16 | 0;
      date = Math.floor(date / 16);
      return (c == "x" ? r : (r & 0x3) | 0x8).toString(16);
    }
  );
  return uniqueId;
}

console.log(createUniqueId());

Answer 37

Anyone who uses Math.random() isn't truly random as it is a pesudorandom generator.

I just discovered this and it is much much better. I recommend a server NodeJS solution (instead of using browser)

// Exists at least Nodejs 16.x.x and above. globalThis.crypto.randomInt is better, more random and support negative range
function randomNumber(min: number, max: number) {
  return globalThis.crypto.randomInt(min, max);
}

https://www.geeksforgeeks.org/node-js-crypto-randomint-method/ The reason it is globalthis. is because I'm using this in NodeJS.

Answer 38

just write use autoincrement

i=1;
getUnique(){
return i++
}