This is a guide on Reactive programming. It begins by explaining to the reader what Reactive programming is and where it is used. Callbacks usually propagate themselves, leading to a callback hell. The reader is guided on how to handle callback hell. Futures and promises, which are very essential in Reactive programming are discussed in detail, thus, you will learn how to use them when programming. Implicit and explicit declarations are also explored in detail. Streams are an important aspect of Reactive programming. This guides explores stream processing in detail, thus, you will learn how...