Generate RFC 4122 compliant UUIDv4

uuidv4.js

/**
 * Generate an RFC 4122 compliant v4uuid using window.crypto.getRandomValues
 * @returns {String} - A newly generated v4uuid
 */
 export function genUuidv4() {
    let hex = window.crypto.getRandomValues(new Uint8Array(128 / 8)); // Or your crypto lib of choice -- Slice off the 0x if lib provides it.
    let bytes = Buffer.from(hex, 'hex');

    // Force byte 7 and 9 to unsigned and pad to 8 bits
    let byte7asBin = (bytes[6] >>> 0).toString(2).padStart(8, "0"); // Get byte 7 as binary
    let byte9asBin = (bytes[8] >>> 0).toString(2).padStart(8, "0"); // Get byte 9 as binary

    // Set High nibble of byte7 to 0100 | 0x04 //
    let byte7Bits = byte7asBin.split('');
    byte7Bits[0] = "0";
    byte7Bits[1] = "1";
    byte7Bits[2] = "0";
    byte7Bits[3] = "0";
    byte7asBin = byte7Bits.join("");

    // Set 2 most significant bits of byte9 to 10 //
    let byte9Bits = byte9asBin.split('');
    byte9Bits[0] = "1";
    byte9Bits[1] = "0";
    byte9asBin = byte9Bits.join("");

    // Inject new bytes //
    bytes[6] = parseInt(byte7asBin, 2); // Byte 7 inject
    bytes[8] = parseInt(byte9asBin, 2); // Byte 9 inject

    let finalHex = bytes.toString('hex');

    // Add hyphens for blocks of 8-4-4-4-12 before returning v4uuid
    let block1 = finalHex.slice(0, 8);
    let block2 = finalHex.slice(8, 12);
    let block3 = finalHex.slice(12, 16);
    let block4 = finalHex.slice(16, 20);
    let block5 = finalHex.slice(20, finalHex.length);
    let v4uuid = [block1, block2, block3, block4, block5].join("-").toLowerCase();

    return v4uuid;
}