I think that the best investment today for any Web developer is to start learning Dart. Why?

As a developer and a university professor, for the first time in my long career, I can do the following with Dart:

I can use Dart both on the client and on the server;

I can apply both object-oriented and functional way of programming;

I can develop in Dart and deploy applications in JavaScript;

I can be a productive developer with many Dart tools and libraries, and get a very good performance in either Dart applications or their JavaScript versions;

I can start developing a prototype without data types and introduce them when I need to convert the prototype to a deployable application;

I can use Dart for both synchronous and asynchronous programming;

I can use many publicly available packages and reuse their libraries;

I can be a web engineer on the client-side and a software engineer on the server-side, with the same language and many reusable libraries.