Read from file and write to file 'Ł' character with nodejs

I have an ansi file with 'Ł' character I would like to read this character and save it to another file with the same encoding(to get 'Ł' character).

const fs = require('fs');
var content = fs.readFileSync('input.txt',null); //Ł
fs.writeFileSync('output.txt',content,null); //Ł how to get this?

How to do this with nodejs?

Update: I checked the input file:

file -i

text/plain charset=uknown-8bit

file -r

Non-ISO extended-ASCII, text with very long lines, with CRLF line terminators

Can I save the file with such details?

I achieved what I wanted by creating binary strings out of buffer with the problematic characters:

const fs = require('fs');
function getChar(charId) {
    let characters = { AA:165, //Ą
         EE:202, //Ę
         CC:198, //Ć
         LL:163, //Ł
         SS:140, //Ś
         OO:211, //Ó
         ZZ:175, //Ż
         ZZZ:143, //Ź
         aa:185, //ą
         ee:234, //ę
         cc:230, //ć
         ll:179, //ł
         ss:156, //ś
         oo:243, //ó
         zz:191, //ź
         zzz:159 //ź
    };
    let buf = new Buffer({
        type:'Buffer',
        data:[ characters[charId] ],
        encoding:'ISO-8859-2'
    });
    return buf.toString('binary')
}
fs.writeFileSync('output.txt',getChar('LL')+" test",'ascii'); //'Ł test'