Change Javascript BLOB encoding to ANSI instead of UTF-8

Question

I was wondering if it is possible to save a simple txt file with Javascript and BLOB with the ANSI encoding.

At this moment I have a script that creates a txt file with CRLF line endings, but with a UTF-8 encoding.

Is it possible to save it with the ANSI encoding? I need this to import the txt file on a 'old' windows program that needs ANSI instead of UTF-8.

This is the example I used: https://jsfiddle.net/UselessCode/qm5AG/

let textFile = null;

function makeTextFile () {
    let text = `Some text with nice line endings\nand special characters like é and ü.`;

    const data = new Blob([text], {
        type: "text/plain",
        endings: "native"
    });

    if (textFile !== null) {
        window.URL.revokeObjectURL(textFile);
    }

    textFile = window.URL.createObjectURL(data);

    return textFile;
}

stackoverflow.com/questions/32510273/… might answer your question - change the charset/encoding hinted to the browser — Thomas Timbul
– Thomas Timbul, Commented Jan 21, 2020 at 12:38

Kaiido · Accepted Answer · 2020-02-16 07:03:25Z

There used to be an option using the TextEncoder API to encode from USVStrings to arbitrary encodings, but this has been removed from specs and browsers.

You'd need to use a library in order to perform the conversion. Here, I'll use inexorabletash/text-encoding:

(async()=> {
const text = `Some text with nice line endings\nand special characters like é and ü.`;
const encoding = 'windows-1252'; // a.k.a ANSI

const encoder = new TextEncoder(encoding, {
  NONSTANDARD_allowLegacyEncoding: true
});
const data = encoder.encode(text); // `data` is an Uint8Array
const encoded_as_ANSI = new Blob([data]);

// for demo only
const encoded_as_UTF8 = new Blob([text]);

const ANSI_read = await readAsText(encoded_as_ANSI, encoding);
const UTF8_read = await readAsText(encoded_as_UTF8, encoding);

console.log("(ANSI)", ANSI_read);
console.log("(UTF8)", UTF8_read);
})();

function readAsText(blob, encoding) {
  return new Promise(res => {
    const reader = new FileReader();
    reader.onload = e => res(reader.result);
    reader.readAsText(blob, encoding);
  });
}

<script>window.TextEncoder = null;// force installation of the polyfill</script>
<script src="https://cdn.jsdelivr.net/gh/inexorabletash/text-encoding/lib/encoding-indexes.js"></script>
<script src="https://cdn.jsdelivr.net/gh/inexorabletash/text-encoding/lib/encoding.js"></script>

However going this route, we loose the endings option, since this applies only to string blobParts.

So one way would be to first create an utf-8 Blob, with the endings option, then convert this UTF-8 blob to ANSI:

(async () => {
  const text = `Some text with nice line endings\nand special characters like é and ü.`;
  const encoding = 'windows-1252'; // a.k.a ANSI

  const utf8_blob = new Blob( [text], { endings: "native" } );
  const utf_8_txt = await utf8_blob.text();

  const encoder = new TextEncoder(encoding, {
    NONSTANDARD_allowLegacyEncoding: true
  });
  const data = encoder.encode(utf_8_txt); // now `data` is an Uint8Array
  const encoded_as_ANSI = new Blob([data]);

  const read_as_ANSI = await readAsText(encoded_as_ANSI, encoding)
  console.log(read_as_ANSI);
})();

function readAsText(blob, encoding) {
  return new Promise(res => {
    const reader = new FileReader();
    reader.onload = e => res(reader.result);
    reader.readAsText(blob, encoding);
  });
}

<script>window.TextEncoder = null;// force installation of the polyfill</script>
<script src="https://cdn.jsdelivr.net/gh/inexorabletash/text-encoding/lib/encoding-indexes.js"></script>
<script src="https://cdn.jsdelivr.net/gh/inexorabletash/text-encoding/lib/encoding.js"></script>

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