Bookmarklet to open the source repository from a github.io page

This is a bookmarklet that jumps to the source code repository when you are viewing a page published using GitHub Pages.

It supports URLs in the format [id].github.io or [id].github.io/[repository].

javascript: (() => {
  const githubIoUrlToRepoUrl = (url) => {
    const m = url.match(/(([^/]+).github.io)\/?([^/]*)/)
    if (!m) {
      return false
    }

    const [, host, githubId, repoPath] = m

    const repo = repoPath || host
    return `http://github.com/${githubId}/${repo}`
  }

  const url = githubIoUrlToRepoUrl(location.href)
  console.log(url)

  if (!url) {
    alert('not github.io repository')
    return
  }
  location.href = url
})()