function uuid() {

    let uuid = "",

        i,

        random;

    for (i = 0; i < 32; i++) {

        random = (Math.random() * 16) | 0;

​

        if (i == 8 || i == 12 || i == 16 || i == 20) {

            uuid += "-";

        }

        uuid += (i == 12 ? 4 : i == 16 ? (random & 3) | 8 : random).toString(16);

    }

    return uuid;

}

​

uuid();

const ui8a = new Uint8Array(1);

function next() {

    let uuid = "", i;

    for (i = 0; i < 32; i++) {

        uuid += (i === 8 || i === 13 || i === 18 || i === 23) ? '-' : (crypto.getRandomValues(ui8a)[0] * 16) | 0;

    }

    return uuid;

}

const ui8a = new Uint8Array(1);

function next() {

    let uuid = [], i;

    for (i = 0; i < 32; i++) {

        uuid.push((i === 8 || i === 13 || i === 18 || i === 23) ? '-' : (crypto.getRandomValues(ui8a)[0] * 16) | 0);

    }

    return uuid.join('');

}