readUInt64BE.js
function readUInt64BE(buf, offset) {
  if (offset){
    buf = buf.slice(offset, offset + 8);
  }
  // create a hex equivalent string:
  let str = buf.toString('hex');
  str = str.split('');
  let solution = 0;
  let mul = 15;
  str.forEach((num) => {
    let dec = getDecimal(num);
    solution += dec * Math.pow(16,mul);
    mul--;
  });
  return solution;        // (value position 0 * 16^15) + (value position 1 * 16^14) + ... +  (value position 7 * 16^0)
}
function readUInt64BE(buf, offset) {
  if (offset){
    buf = buf.slice(offset, offset + 8);
  }
  // create a hex equivalent string:
  let str = buf.toString('hex');
  str = str.split('');
  let solution = 0;
  let mul = 15;
  str.forEach((num) => {
    let dec = getDecimal(num);
    solution += dec * Math.pow(16,mul);
    mul--;
  });
  return solution;        // (value position 0 * 16^15) + (value position 1 * 16^14) + ... +  (value position 7 * 16^0)
}
readInt32BE(value, number[, offest])