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 digi

Answer 1

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 2

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 3

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

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

Answer 4

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

sample result "k3jobnvt_15750033412250_18299601769317408"

Answer 5

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 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.