BigQuery UDF Convert Bytes to Hex & Hex to UUID

bytes-to-uuid.sql

CREATE TEMP FUNCTION BytesToUUID(data BYTES)
  RETURNS STRING 
  LANGUAGE js AS """
  const tableStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  const atob = function (base64) {
    if (/(=[^=]+|={3,})$/.test(base64)) throw new Error("String contains an invalid character");
    base64 = base64.replace(/=/g, "");
    var n = base64.length & 3;
    if (n === 1) throw new Error("String contains an invalid character");
    for (var i = 0, j = 0, len = base64.length / 4, bin = []; i < len; ++i) {
      var a = tableStr.indexOf(base64[j++] || "A"), b = tableStr.indexOf(base64[j++] || "A");
      var c = tableStr.indexOf(base64[j++] || "A"), d = tableStr.indexOf(base64[j++] || "A");
      if ((a | b | c | d) < 0) throw new Error("String contains an invalid character");
      bin[bin.length] = ((a << 2) | (b >> 4)) & 255;
      bin[bin.length] = ((b << 4) | (c >> 2)) & 255;
      bin[bin.length] = ((c << 6) | d) & 255;
    };
    return String.fromCharCode.apply(null, bin).substr(0, bin.length + n - 4);
  };
  
  const base64ToHex = function(str) {
    const raw = atob(str);
    let result = '';
    for (let i = 0; i < raw.length; i++) {
      const hex = raw.charCodeAt(i).toString(16);
      result += (hex.length === 2 ? hex : '0' + hex);
    }
    return result.toLowerCase();
  }
  
  //if all you need is the hex, skip the UUID below
  const hex = base64ToHex(data);
  //convert hex to UUID
  return [
    hex.substring(0, 8),
    hex.substring(8, 12),
    hex.substring(12, 16),
    hex.substring(16, 20),
    hex.substring(20)
  ].join('-')
""";


SELECT BytesToUUID(FROM_BASE64('IFdkTmmzT92YkDYQiV/zmQ=='));

This link on SO was very helpful: https://stackoverflow.com/questions/23190056/hex-to-base64-converter-for-javascript/41797377