Promise - document ready

docready.js

HTMLDocument.prototype.ready = function () {
  return new Promise(function(resolve, reject) {
    if (document.readyState === 'complete') {
      resolve(document);
    } else {
      document.addEventListener('DOMContentLoaded', function() {
      resolve(document);
    });
          }
  });
}
document.ready().then(function () {
  console.log('Done! xD');
});