What is RxJS?

RxJS (Reactive Extensions for JavaScript) is a library for reactive programming using observables that makes it easier to compose asynchronous or callback-based code. RxJS provides an implementation of the Observable type.

RxJS offers a number of functions that can be used to create new observables. These functions can simplify the process of creating observables from things such as events, timers, promises, and so on.

RxJS Observables

RxJS stands for Reactive Extension for JavaScript. As the name implied RxJS is used to implement reactive programming in JavaScript. Reactive programming deals with implementing asynchronous streams. RxJS provides an implementation of Observable type which is used in Angular to implement a producer – subscriber pattern.

An observable is a function that produces a stream of values and emits it to its subscribers over time. When you subscribe to an observable, you are an observer. Observer receive the emitted values.

Observables can emit 3 types of notifications

next – To emit the next value in the list
complete – When the observable is done with emitting all the values
error – When an error occurred in the observable.

We can understand how the observables and observer work with a simple example as follows.