Type script does a very good job not to hide the underlying platform. In it's essence it is just a development time linter and does not interfere with the JavaS

Type script does a very good job not to hide the underlying platform. In it's essence it is just a development time linter and does not interfere with the JavaScript runtime at all (except enums). And I think that's actually the reason why it won the competition against Googles Dart. They even used Microsofts TypeScript for Angular instead of their own language Dart.