Understanding RxJS Observables and why you need them

RxJS is a framework for reactive programming that makes use of Observables, making it really easy to write asynchronous code. According to the official documentation, this project is a kind of reactive extension to JavaScript with better performance, better modularity, better debuggable call stacks, while staying mostly backwards compatible, with some breaking changes that reduce the API surface. It is the official library used by Angular to handle reactivity, converting pull operations for call-backs into Observables.