The RxJS team has announced their 6.0 release, which improves the project's approach to modularity, streamlines performance, adds a backward compatibility package to ease upgrades, and supports code migration for TypeScript users.
To streamline migration from RxJS 5 to 6, the rxjs-compat package provides a compatibility layer between these versions.
RxJS 6 and the compatibility layer can be installed via npm:
npm install rxjs@6 rxjs-compat@6 --save
The compatibility shim makes it possible to upgrade to version 6 with no code changes, but developers should then update their source code to reduce the source bundle size for RxJS before deploying their applications to production.
Angular 6 users can also benefit from the RxJS schematic, making it possible to leverage Angular 6's ng update mechanism which will automatically install rxjs-compat into an application.
Module import paths were reorganized into several categories:
- rxjs: Creation methods, types, schedulers, and utilities
- rxjs/ajax: RxJS HTTP request implementation
- rxjs/operators: Pipeable RxJS operators
- rxjs/testing: RxJS testing utilities
- rxjs/webSocket: RxJS WebSocket implementation
TypeScript users of RxJS are encouraged to use rxjs-tslint which will help refactor import paths from version 5 to 6.
The other significant change in RxJS is the transition to using a pipeable API for its operators. Previously RxJS provided chaining which would patch the prototype operator, but this introduced challenges as it was global, challenging to optimize for webpack's tree-shaking capabilities, and challenging for linting tools.
For example, the following is an RxJS 5 example:
source
.map(x => x + x)
.mergeMap(n => of(n + 1, n + 2)
.filter(x => x % 1 == 0)
.scan((acc, x) => acc + x, 0)
)
.catch(err => of('error found'))
.subscribe(printResult);
In RxJS 6, it changes to:
source.pipe(
map(x => x + x),
mergeMap(n => of(n + 1, n + 2).pipe(
filter(x => x % 1 == 0),
scan((acc, x) => acc + x, 0),
)),
catchError(err => of('error found')),
).subscribe(printResult);
RxJS project lead Ben Lesh recently spoke about RxJS 6, providing the motivation behind the changes in the project.
RxJS is a library for reactive programming using Observables to compose asynchronous or callback-based code. Efforts have started to standardize the Observable portion of RxJS as part of a future version of JavaScript, but the Observable proposal has not yet gained traction.
RxJS is available under the Apache 2 License. Learn more at the RxJS website. Contributions are welcome via the RxJS GitHub project.
