In previous article, I have explained about Uniqueidentifier (GUID/UUID) in SQL Server, now in this article, I am going to provide few possible ways to generate GUID / UUID using Javascript.

GUID (Globally Unique Identifier) or (UUID) Universally Unique Identifier is a 16 byte binary value and are identifiers designed to provide certain uniqueness guarantees.

Generate GUID using Math.Random()

To generate GUID using Math.Random() in Javascript, you can use the below code.

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);
  });
}

Since, GUID created above is highly relies on Math.Random(), which can be good source of creating GUID, but it cannot considered as high-quality Random Number generator.

So, there can be chance of Collisions of GUID, but can be used to small number of generation and we will move on to next method.

A better implementation of Math.Random() to generate GUID would be to use Date and Time with it, so it can be unique.

So, here is the Javascript code for it

function generateUUIDUsingMathRandom() { 
    var d = new Date().getTime();//Timestamp
    var d2 = (performance && performance.now && (performance.now()*1000)) || 0;//Time in microseconds since page-load or 0 if unsupported
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
        var r = Math.random() * 16;//random number between 0 and 16
        if(d > 0){//Use timestamp until depleted
            r = (d + r)%16 | 0;
            d = Math.floor(d/16);
        } else {//Use microseconds since page-load if supported
            r = (d2 + r)%16 | 0;
            d2 = Math.floor(d2/16);
        }
        return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
    });
}

generate-guid-javascript-min.png

Sample Output, when above code is used

56648260-754f-4f09-b256-a73124f12c21

1aa3bdae-974f-4455-97f6-316f75f20464

Here is the complete JS fiddle

Generate GUID using Crypto API in JS

The Crypto interface represents basic cryptography features available in the current context.

It allows access to a cryptographically strong random number generator and to cryptographic primitives, so here is Javascript sample code to generate GUID using it.

function uuidv4() {
  return ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, c =>
    (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
  );
}

GUID using Pseudo-Random Number

Here is another example

function createUUID() {
    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;
}

There are many other ways, but these are best one which you can use to generate GUID using Javascript.

If you are considering any of the above solution, then I would recommend you to use, Math.Random with Datetime generator, which will make sure that no 2 GUID can be same.

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