rxjs-interop

What is it?

A package that contains interop helper functions and types for use with RxJS.

Why might you need it?

Observables exist independently of RxJS. There are TC39 and WHATWG observable proposals. The helpers in this package make it easy to implement observables that will work with or without RxJS and will still play nice - with RxJS - if Symbol.observable is not configured.

For more information on RxJS interop, see this blog post.

This package has no dependency on RxJS and is small, but if you want to publish an interop package with no dependencies, just copy the license and the code from this project into yours.

Install

Install the package using NPM:

npm install rxjs-interop --save

Usage

Interop observables expose an observable factory via the Symbol.observable property, like this:

export const interop = {
  [Symbol.observable]: () => {
    return {
      subscribe(nextOrObserver, error, complete) {
        /* figure out whether it's a next callback or an observer */
        /* call observer methods */
        return () => { /* some teardown logic */ };
      }
    };
  }
});

For this to work with RxJS, the caller will need to initialize Symbol.observable - which makes things more complicated.

You can use the toObserver and patch helpers in this package to more easily implement subscribe and to make sure that the interop observable will work with RxJS without Symbol.observable having to be initialized:

import { patch, toObserver } from "rxjs-interop";

export const interop = patch({
  [Symbol.observable]: () => {
    return {
      subscribe(nextOrObserver, error, complete) {
        const observer = toObserver(nextOrObserver, error, complete);
        /* call observer methods */
        return () => { /* some teardown logic */ };
      }
    };
  }
});

patch can be passed either an interop observable instance or the constructor of an interop observable class - see the tests for usage.

For an example of how this package can be used to implement things that can be used with or without RxJS, check out Christoph Guttandin's subscribable-things.