Marco Alka

Tested Result: 여보세요 -> 占싼됰궖占쎈챷��

and file type still UTF-8

Just use your favorite text editor, open a document and change the encoding. Personally, I use Kate, but it should be the same for Notepad++.

If you want to do so in NodeJS (taking your tag into consideration), WriteFile exposes an option parameter, which you can use to set the encoding:

require('fs').writeFile(
  'message.txt',
  '여보세요',
  'euc-kr',
  () => { console.log('done') }
);

If you need conversion in a browser, there's a library for that (tm):

// untested!

const uint8array = new TextEncoder().encode('여보세요');
const str = new TextDecoder('euc-kr').decode(uint8array);
const blob = new Blob([str], { type: 'text/plain;charset=euc-kr' });

FileSaver.saveAs(blob, "hello world.txt");