I'm using this code snippet:

// The gh instance is Github object property on window authorized with a personal access token.
var repo = gh.getRepo("TomasHubelbauer", "TomasHubelbauer.Github.io")
repo.write("master", "Test.md", "# Test", "Create Test.md programatically", function (err)
{
  console.log(err);
});

When examining the Network tab, first I see 204 OPTIONS with no content returned and then 404 GET, both to:
https://api.github.com/repos/TomasHubelbauer/TomasHubelbauer.Github.io/contents/Test.md?…

The file doesn't exist and I'm trying to create it for the first time.

Is it possible that my personal access token is too restrictive and doesn't offer write access or something? Currently it has only the public_repo scope, which I thought should be enough.

I also get Uncaught TypeError: btoa is not a function on github.js:667.

Will investigate further, just putting this out there in case someone experienced this.