Javascript: create UTF-16 text file?

Question

I have some string need to be a UTF-16 text file. For example:

var s = "aosjdfkzlzkdoaslckjznx";
var file = "data:text/plain;base64," + btoa(s);

This will result a UTF-8 encoding text file. How can I get a UTF-16 text file with string s?

Does your file need to be in a data: URL? 'cause you can easily do what you want with a Blob. — Touffy
– Touffy, Commented Oct 4, 2015 at 18:50
Yes, I need base64. But I don't like fileReaderAPI because it's asynchronous. It will make my app too complex. Do you have better suggestion? — Wilson Luniz
– Wilson Luniz, Commented Oct 4, 2015 at 19:20
I suggest you reevaluate your criteria. Web apps use async stuff, it's inevitable. But as it happens, using TextEncoder and creating a Blob URI won't be async. You don't need the File API because you're not reading a file, you're creating one. — Touffy
– Touffy, Commented Oct 4, 2015 at 20:49
I use the arrayBuffer directly convert to base64 with this: stackoverflow.com/questions/9267899/… — Wilson Luniz
– Wilson Luniz, Commented Oct 4, 2015 at 21:01

Community · Accepted Answer · 2017-05-23 12:09:59Z

13

Related: Javascript to csv export encoding issue

This should do it:

document.getElementById('download').addEventListener('click', function(){

	downloadUtf16('Hello, World', 'myFile.csv')
});

function downloadUtf16(str, filename) {

	// ref: https://stackoverflow.com/q/6226189
	var charCode, byteArray = [];

	// BE BOM
  byteArray.push(254, 255);

	// LE BOM
  // byteArray.push(255, 254);

  for (var i = 0; i < str.length; ++i) {
  
    charCode = str.charCodeAt(i);
    
    // BE Bytes
    byteArray.push((charCode & 0xFF00) >>> 8);
    byteArray.push(charCode & 0xFF);
    
    // LE Bytes
    // byteArray.push(charCode & 0xff);
    // byteArray.push(charCode / 256 >>> 0);
  }
  
  var blob = new Blob([new Uint8Array(byteArray)], {type:'text/plain;charset=UTF-16BE;'});
  var blobUrl = URL.createObjectURL(blob);
  
	// ref: https://stackoverflow.com/a/18197511
  var link = document.createElement('a');
  link.href = blobUrl;
  link.download = filename;

  if (document.createEvent) {
    var event = document.createEvent('MouseEvents');
    event.initEvent('click', true, true);
    link.dispatchEvent(event);
  } else {
    link.click();
  }
}

<button id="download">Download</button>

edited May 23, 2017 at 12:09

CommunityBot

11 silver badge

answered Mar 29, 2017 at 16:52

skibulk

3,2181 gold badge39 silver badges43 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

LocalHorst Over a year ago

Does the trick for me! but, in your example you are working with BE BOM, but encode your blob with charset UTF-16LE. Shouldn't that be UTF-16BE then?

thejoin Over a year ago

You save my life.

Sebastian Over a year ago

Does this also work for Unicode surrogate pairs (see the charCodeAt and codePointAt documentation), i.e. characters/emojis with a unicode value greater than 0xFFFF?

Touffy · Accepted Answer · 2017-03-27 15:42:36Z

1

You can use a legacy polyfill of the native TextEncoder API to transform a JavaScript string into an ArrayBuffer. As you'll see in that documentation, UTF16 with either endianness is was supported. Libraries that provide UTF-16 support in a Text-Encoder-compatible way will probably appear soon, if they haven't already. Let's assume that one such library exposes a constructor called ExtendedTextEncoder.

Then you can easily create a Blob URL to allow users to download the file, without the inefficient base-64 conversion.

Something like this:

s = "aosjdfkzlzkdoaslckjznx"
var encoder = new ExtendedTextEncoder("utf-16be")
var blob = new Blob(encoder.encode(s), "text/plain")
var url = URL.createObjectURL(blob)

Now you can use url instead of your data: URL.

edited Mar 27, 2017 at 15:42

answered Oct 4, 2015 at 18:55

Touffy

6,63626 silver badges31 bronze badges

6 Comments

Wilson Luniz Over a year ago

Just note, UTF-16LE text file has a magic header(FF,FE or 255,254). See: en.wikipedia.org/wiki/…

Wilson Luniz Over a year ago

I'm sorry but I found this doesn't works in Safari. Safari just doesn't support TextEncoder() . Is there any other solution for Safari?

Touffy Over a year ago

You can use a polyfill for TextEncoder. I can recommend the one I linked, I've used it myself. It will create a TextEncoder object that behaves just like the native one (only if it's not avaialble natvely).

Wilson Luniz Over a year ago

Oh this is my first time heard about polyfill. Thanks and it works!

skibulk Over a year ago

TextEncoder does not accept an encoding string as a parameter any more: developer.mozilla.org/en-US/docs/Web/API/TextEncoder/…

|

Collectives™ on Stack Overflow

Javascript: create UTF-16 text file?

2 Answers 2

3 Comments

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related