rxjs

What is rxjs?

RxJS (Reactive Extensions for JavaScript) is a library for reactive programming using Observables, to make it easier to compose asynchronous or callback-based code. It provides an API for asynchronous programming with observable streams.

What are rxjs's main functionalities?

Creating Observables

This feature allows you to create an Observable stream of data. The code sample demonstrates how to create an Observable that emits several values over time.

const { Observable } = require('rxjs');

const observable = new Observable(subscriber => {
  subscriber.next(1);
  subscriber.next(2);
  subscriber.next(3);
  setTimeout(() => {
    subscriber.next(4);
    subscriber.complete();
  }, 1000);
});

Subscribing to Observables

This feature allows you to subscribe to an Observable and react to the data being emitted. The code sample shows how to subscribe to an Observable created from an array.

const { from } = require('rxjs');

const observable = from([10, 20, 30]);
const subscription = observable.subscribe(x => console.log(x));

Operators

Operators are methods on the Observable type that allow for composing asynchronous operations in a declarative manner. The code sample demonstrates the use of 'filter' and 'map' operators to process data.

const { of } = require('rxjs');
const { map, filter } = require('rxjs/operators');

const nums = of(1, 2, 3, 4, 5);
const squaredNums = nums.pipe(
  filter(n => n % 2 !== 0),
  map(n => n * n)
);
squaredNums.subscribe(x => console.log(x));

Handling Errors

This feature allows you to handle errors in an Observable sequence. The code sample demonstrates how to catch and handle errors using the 'catchError' operator.

const { throwError, of } = require('rxjs');
const { catchError } = require('rxjs/operators');

const observable = throwError(new Error('Something went wrong!'));
const handled = observable.pipe(
  catchError(error => of(`Caught: ${error.message}`))
);
handled.subscribe(x => console.log(x), err => console.error(err));

Combining Observables

This feature allows you to combine multiple Observables into one. The code sample demonstrates how to use 'combineLatest' to combine two streams of data.

const { combineLatest, of } = require('rxjs');

const temperature = of(70, 72, 76, 79, 75);
const humidity = of(40, 44, 49, 58, 55);

const combined = combineLatest([temperature, humidity]);
combined.subscribe(([temp, hum]) => console.log(`Temperature: ${temp} Humidity: ${hum}`));

Other packages similar to rxjs

most

Most.js is a high-performance reactive programming library. It offers similar functionality to RxJS but focuses on providing a smaller, faster, and more modular library.

bacon.js

Bacon.js is a functional reactive programming library for JavaScript. It is similar to RxJS in that it provides Observables and a rich collection of operators to work with asynchronous data streams, but it has a different API design and implementation.

xstream

XStream is a library for building asynchronous and event-based programs using observable streams. It is similar to RxJS but with a focus on simplicity and minimalism, offering a smaller set of operators.

kefir

Kefir.js is a Reactive Programming library with a focus on high performance and low memory usage. It is similar to RxJS but is more lightweight and has a slightly different API.