How to convert uploaded file from charset=iso-8859-1 to charset=utf-8?

Question

When user uploads a file that has charset=iso-8859-1 it comes with question marks and gibberish.

I have seen that there online web converts it successfully to utf-8 - so after uploading the file after this conversion the file is getting uploaded properly. This is the web: https://subtitletools.com/convert-text-files-to-utf8-online

This is my code:

const file = document.getElementById('some-id').files[0];

const reader = new FileReader();

reader.onloadend = event => {
  let data = event.target.result;
  console.log(`[data]:`, data); // question marks / gibberish
}

reader.readAsText(file);

I have also tried to use reader.readAsBinaryString but got gibberish instead of question marks.

I have also tried to use the utf8 library: https://www.npmjs.com/package/utf8 but it didn't work.

How the site that I mentioned above achieves to convert the file to the desired charset so its data is not in question marks or gibberish? BTW also Google Drive does it well.

Answer 1

You can use TextDecoder with you own charset

var data = new TextDecoder('iso-8859-1').decode(await file.arrayBuffer())

guess the harder part is to figure out what charset it's

If you are not using async/await then you can instead do this:

const file = document.getElementById('some-id').files[0];
file.arrayBuffer().then(ab => {
  const data = new TextDecoder('iso-8859-1').decode(ab)
})