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)
}
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])
readInt32BE ( value number [ offest ] )