Unraveling the Mysteries of Reactive Programming
Introduction
Reactive programming is a paradigm that allows us to manage asynchronous data streams with ease. At its core, it’s about writing programs that react to changes in data streams. RxJS is a popular library that enables us to write reactive programs with a functional approach.
What is Observable?
An Observable is the heart of RxJS. It’s a collection of future values or events that can be subscribed to. Think of it like an array whose items arrive asynchronously. When we subscribe to an Observable, it starts working, and we can receive values, errors, or completion notifications.
The Observer Pattern
An Observer is a collection of callback functions that react to values arriving via an Observable. It consists of three callback methods: next, error, and complete. The subscribe method returns a Subscription, which allows us to unsubscribe from the Observable.
Reverse Engineering Observable
Let’s create an Observable class using TypeScript classes and interfaces. We’ll define an Observer interface, a Subscription class, and an Observable class with a subscribe method. We’ll also create a create static method to create new Observables.
Creation Operators
RxJS provides creation operators like fromEvent and of to create Observables from different inputs. We can rewrite these operators using our Observable and Subscription classes. For example, let’s recreate the of operator, which takes multiple values as input and pushes them to the observer.
Pipeable Operators
Pipeable operators allow us to modify the original Observable using functional programming. We can create custom pipeable operators by understanding their structure and anatomy. Let’s create a filter operator that takes a predicate function as input and returns a new Observable.
The Pipe Method
The pipe method takes single or multiple operators as input and returns a new Observable. We can reverse engineer the pipe method by looping over the operators and applying them to the source Observable.
Final Example
Let’s create and consume an Observable using our reverse-engineered library. We can switch the imports to RxJS library, and everything will work fine.
Takeaway
In this article, we’ve explored the world of reactive programming, Observables, and RxJS. We’ve learned about the Observer pattern, creation operators, and pipeable operators. By reverse engineering RxJS, we’ve gained a deeper understanding of its inner workings.