Question

69

Saving a Uint8Array to a binary file

rated 0 times [ 73] [ 4] / answers: 1 / hits: 28423 / 10 Years ago, sun, august 17, 2014, 12:00:00

I am working on a web app that opens binary files and allows them to be edited.

This process is basically ondrop -> dataTransfer.files[0] -> FileReader -> Uint8Array

Essentially, I want to be able to save the modified file back as a binary file. Ideally as a file download with a specified file name.

There doesn't seem to be any standard method of doing this, and that sucks, because everything up to that point is well supported.

I am currently converting the array to a string using String.fromCharCode(), base64 encoding that, and using a data uri in a hyperlink like data:application/octet-stream;base64,.., along with the download attribute to specify filename.

It seems to work, but it's quite hacky and I think converting the raw bytes to a string might introduce encoding issues depending on the byte values. I don't want the data to become corrupt or break the string.

Barring that, is there a better/proper method for getting an array of bytes as a binary file to the user?

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kalias

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2 Years ago

answered 10 Years ago kourtney · Accepted Answer

These are utilities that I use to download files cross-browser. The nifty thing about this is that you can actually set the download property of a link to the name you want your filename to be.

FYI the mimeType for binary is application/octet-stream

var downloadBlob, downloadURL;



downloadBlob = function(data, fileName, mimeType) {

  var blob, url;

  blob = new Blob([data], {

    type: mimeType

  });

  url = window.URL.createObjectURL(blob);

  downloadURL(url, fileName);

  setTimeout(function() {

    return window.URL.revokeObjectURL(url);

  }, 1000);

};



downloadURL = function(data, fileName) {

  var a;

  a = document.createElement('a');

  a.href = data;

  a.download = fileName;

  document.body.appendChild(a);

  a.style = 'display: none';

  a.click();

  a.remove();

};

Usage:

downloadBlob(myBinaryBlob, 'some-file.bin', 'application/octet-stream');