Async load of Github's gists without jquery in 31 lines of code

gists.js

(function(){
  var gists = document.getElementsByTagName('gist');
  function embed(id, file, i, tag) {
    window['embed_gist_' + i] = function(gist) {
      var div = document.createElement('div');
      div.innerHTML = gist.div;
      tag.parentNode.replaceChild(div.firstChild, tag);

      var css = document.createElement('link');
      css.rel = 'stylesheet';
      css.href = gist.stylesheet;
      document.head.appendChild(css);
    };
    var url = 'https://gist.github.com/' + id + '.json?callback=embed_gist_' + i;
    if (file) {
      url += '&file=' + file;
    }
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.src = url;
    document.head.appendChild(script);
  }
  for (var i = 0; i < gists.length; i++) {
    var id = gists[i].getAttribute('data-id');
    var file = gists[i].getAttribute('data-file');
    embed(id, file, i, gists[i]);
  }
})();