André shows us how to build a minimum functioning RxJS and teaches us some important concepts about reactive programming. JavaScript has multiple APIs that use callback functions that all do nearly the same thing with slight variations. Event listeners, array methods such as `.forEach`, promises, and NodeJS streams all are very close in the way they are written. Instead, in RxJS you'd unify all of these APIs under one abstraction. [Toy Rx](https://github.com/staltz/toy-rx) is an interesting library to go beyond this livestream.