ReactiveX – An API for asynchronous programming with observable streams
ReactiveX is a library for composing asynchronous and event-based programs by using observable sequences.
It extends the observer pattern to support sequences of data and/or events and adds operators that allow you to compose sequences together declaratively while abstracting away concerns about things like low-level threading, synchronization, thread-safety, concurrent data structures, and non-blocking I/O.
ReactiveX is more than an API, it’s an idea and a breakthrough in programming. It has inspired several other APIs, frameworks, and even programming languages.