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?
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.getFullMonth < 9 ? '0' : '') + now.getFullMonth().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()
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.
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
This can be achieved simply with the following code:
var date = new Date();
var components = [
date.getYear(),
date.getMonth(),
date.getDate(),
date.getHours(),
date.getMinutes(),
date.getSeconds(),
date.getMilliseconds()
];
var id = components.join("");
Here's what I do when I want something smaller than a bunch of numbers - change base.
var uid = (new Date().getTime()).toString(36)
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.
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.
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
This should do :
var uniqueNumber = new Date().getTime(); // milliseconds since 1st Jan. 1970
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"
This also should do:
(function() {
var uniquePrevious = 0;
uniqueId = function() {
return uniquePrevious++;
};
}());
Posting this code snippet here for my own future reference (not guaranteed but satisfactory "unique" enough):
// a valid floating number
window.generateUniqueNumber = function() {
return new Date().valueOf() + Math.random();
};
// a valid HTML id
window.generateUniqueId = function() {
return "_" + new Date().valueOf() + Math.random().toFixed(16).substring(2);
};
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++;
};
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
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
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() )
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console.log( (new Date()).getTime() ); console.log( (new Date()).getTime() )
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VM1156:1 1469615398846
console.log( (new Date()).getTime() ); console.log( (new Date()).getTime() )
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Second we try the proposed solution that avoid collisions in the 1/1000 window:
console.log( window.mwUnique.getUniqueID() ); console.log( window.mwUnique.getUniqueID() );
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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
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use this:for creating unique number in javascript
var uniqueNumber=(new Date().getTime()).toString(36);
It really works. :)
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();
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();
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;
}
Easy and always get unique value :
const uniqueValue = (new Date()).getTime() + Math.trunc(365 * Math.random());
**OUTPUT LIKE THIS** : 1556782842762
来源：https://stackoverflow.com/questions/8012002/create-a-unique-number-with-javascript-time