Hi Philip,
thanks for the hint with the ByteArray.
 
    const ByteArray = imports.byteArray;
 
    let a = new ByteArray.ByteArray();
    let b = new ByteArray.ByteArray();
 
    a[0] = 97;
    a[1] = 98;
 
    b[0] = 'a' ;
    b[1] = 'b' ;
 
    print(a);
    print(b);
 
prints
  ab
  <blank>
 
Haven't figured out how to solve it yet...