It uses babel, so it uses regenerator ( <a href="https:&#x2F;&#x2F;github.com&#x2F;facebook&#x2F;regenerator" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;facebook&#x2F;regenerator</a> ) and then uglify probably.<p>It will be great when typescript can do it natively because it knows at lot more before the being translated to javascript : <a href="https:&#x2F;&#x2F;github.com&#x2F;Microsoft&#x2F;TypeScript&#x2F;issues&#x2F;8" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;Microsoft&#x2F;TypeScript&#x2F;issues&#x2F;8</a>