function injectStylesheet(stylesheetName) {
  var link = document.createElement('link');
  link.setAttribute('rel', 'stylesheet');
  link.setAttribute('href', stylesheetName);
  document.head.appendChild(link);
}

function injectStyles(css) {
  injectStylesheet('data:text/css;charset=UTF-8,' + encodeURIComponent(css));
}

function injectScript(scriptName) {
  var script = document.createElement('script');
  script.src = scriptName;
  document.head.appendChild(script);
}

function escapeUsername(username) {
  var quoteRegex = /"/g;
  var commentRegex = /<!---->/g;
  return username.replace(quoteRegex, '\\"').replace(commentRegex, '');
}