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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.
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}`));
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.
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.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.
Reactive Extensions Library for JavaScript. This is a rewrite of Reactive-Extensions/RxJS and is the latest production-ready version of RxJS. This rewrite is meant to have better performance, better modularity, better debuggable call stacks, while staying mostly backwards compatible, with some breaking changes that reduce the API surface.
Most PRs should be made to master, unless you know it is a breaking change.
By contributing or commenting on issues in this repository, whether you've read them or not, you're agreeing to the Contributor Code of Conduct. Much like traffic laws, ignorance doesn't grant you immunity.
npm install rxjs
To import the entire core set of functionality:
import Rx from 'rxjs/Rx';
Rx.Observable.of(1,2,3)
To import only what you need by patching (this is useful for size-sensitive bundling):
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';
import 'rxjs/add/operator/map';
Observable.of(1,2,3).map(x => x + '!!!'); // etc
To import what you need and use it with proposed bind operator:
Note: This additional syntax requires transpiler support and this syntax may be completely withdrawn from TC39 without notice! Use at your own risk.
import { Observable } from 'rxjs/Observable';
import { of } from 'rxjs/observable/of';
import { map } from 'rxjs/operator/map';
Observable::of(1,2,3)::map(x => x + '!!!'); // etc
To install this library for CommonJS (CJS) usage, use the following command:
npm install rxjs
Import all core functionality:
var Rx = require('rxjs/Rx');
Rx.Observable.of(1,2,3); // etc
Import only what you need and patch Observable (this is useful in size-sensitive bundling scenarios):
var Observable = require('rxjs/Observable').Observable;
// patch Observable with appropriate methods
require('rxjs/add/observable/of');
require('rxjs/add/operator/map');
Observable.of(1,2,3).map(function (x) { return x + '!!!'; }); // etc
Import operators and use them manually you can do the following (this is also useful for bundling):
var of = require('rxjs/observable/of').of;
var map = require('rxjs/operator/map').map;
map.call(of(1,2,3), function (x) { return x + '!!!'; });
You can also use the above method to build your own Observable and export it from your own module.
To install this library via npm version 3, use the following command:
npm install @reactivex/rxjs
This will include CJS/Global builds and can be used for all module types.
If you are using npm version 2 before this library has achieved a stable version, you need to specify the library version explicitly:
npm install @reactivex/rxjs@5.0.0
For CDN, you can use unpkg:
https://unpkg.com/rxjs@version/bundles/Rx.min.js
replace version with the current version. See docs.
var Rx = require('@reactivex/rxjs');
Rx.Observable.of('hello world')
.subscribe(function(x) { console.log(x); });
The build and test structure is fairly primitive at the moment. There are various npm scripts that can be run:
src/
to dist/es6
dist/es6
to dist/cjs
dist/es6
to dist/amd
dist/cjs
to dist/global/Rx.js
jasmine
protractor
dist/es6
to dist/docs
istanbul
code coverage against test casesjasmine
, must have built prior to running.npm run info
will list available script.
# build all the things!
npm run build_all
Run npm run build_perf
or npm run perf
to run the performance tests with protractor
.
Run npm run perf_micro
to run micro performance test benchmarking operator.
RxNext uses ESDoc to generate API documentation. Refer to ESDoc's documentation for syntax. Run npm run build_docs
to generate.
The script npm run tests2png
requires some native packages installed locally: imagemagick
, graphicsmagick
, and ghostscript
.
For Mac OS X with Homebrew:
brew install imagemagick
brew install graphicsmagick
brew install ghostscript
mkdir -p /usr/local/share/ghostscript && tar zxvf /path/to/ghostscript-fonts.tar.gz -C /usr/local/share/ghostscript
For Debian Linux:
sudo add-apt-repository ppa:dhor/myway
apt-get install imagemagick
apt-get install graphicsmagick
apt-get install ghostscript
For Windows and other Operating Systems, check the download instructions here:
FAQs
Reactive Extensions for modern JavaScript
The npm package rxjs receives a total of 34,276,007 weekly downloads. As such, rxjs popularity was classified as popular.
We found that rxjs demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 3 open source maintainers collaborating on the project.
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Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
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