Tested with "Firefox 38.0" and "Chromium Version 38.0.2125.101 Built on jessie/sid, running on Debian jessie/sid (290379)". When trying to write to a new file, I get an error about btoa not found.

var github = new Github({
    token: token,
    auth: "oauth"
});
var repo = github.getRepo(user, reponame);
repo.write('master', 'data', "Hola", "First", function(err) {});

The error happens in the repo.write line. If instead of that one I have the wollowing one:

repo.show(showRepo);

It calls showRepo, which is a function that shows the info about the repo perfectly.

After a bit of debugging, it seems that the problem is that btoa is not available at the moment of calling "write", but is needed by it.

Changing all invoking occurences of "btoa" to "window.btoa" in github.js, (three occurrences in total) fixes this. But I'm not sure this is the best way of fixing it, since it will probably not run if not in a browser... In addition, I see the code

  if (typeof exports !== 'undefined') {
      XMLHttpRequest = require('xmlhttprequest').XMLHttpRequest;
      _ = require('underscore');
      var btoa = require('btoa'); //jshint ignore:line
  } else { 
      _ = window._; 
  }

which maybe is set up for exactly this scenario, but I'm not sure why it is not working.