RxJS Lite (Legacy v4)

4.0.8 · abandoned · verified Tue Apr 21

rx-lite is a lightweight distribution of the Reactive Extensions for JavaScript (RxJS) version 4.x, primarily used for composing asynchronous and event-based operations in JavaScript. At version 4.0.8, it provided a core set of observable operators for handling events, promises, callbacks, and time-based operations in both modern browser environments (IE9+) and Node.js. The library was part of an earlier generation of RxJS, with its development repository transitioning to 'RxJS vNext' (which became RxJS v5 and later) after the 4.x series. This version prioritizes a compact bundle (`rx.lite.js`) for everyday use cases, differing from the more modular, tree-shakable approach adopted in subsequent major RxJS releases. It had an irregular release cadence, focusing on bug fixes and performance improvements within the 3.x and 4.x lines before the major architectural shift to modern RxJS.

Common errors

```
TypeError: (0, _rxLite.Observable) is not a constructor
```
cause Attempting to use ES module import syntax (`import { Observable } from 'rx-lite';`) with a CommonJS-only package.

fix Use CommonJS `require`: `const Rx = require('rx-lite'); const Observable = Rx.Observable;`
```
ReferenceError: require is not defined
```
cause Using `require('rx-lite')` directly in a browser environment without a CommonJS bundler (like Webpack or Browserify).

fix For browser usage, include the `rx.lite.js` file via a `<script>` tag. For bundled applications, ensure your bundler is correctly configured to handle CommonJS modules.
```
ReferenceError: Rx is not defined
```
cause Trying to use `Rx` in the browser without loading the `rx.lite.js` script, or in Node.js without `require('rx-lite')`.

fix Ensure `rx.lite.js` is loaded via a `<script>` tag before your code, or add `const Rx = require('rx-lite');` at the top of your Node.js file.

Warnings

breaking This `rx-lite` package is for RxJS v4. Development transitioned to 'RxJS vNext' (modern `rxjs` v5+), which introduced significant breaking changes, API rewrites, and a new modular import system. `rx-lite` is not compatible with modern RxJS.
Fix: Migrate to the current `rxjs` package (`npm install rxjs`). This involves rewriting import statements and potentially many operator calls due to API changes.
gotcha RxJS v4, including `rx-lite`, primarily targets CommonJS for Node.js and global script tags for browsers. It does not support native ES Modules (ESM) `import` syntax, which will lead to errors.
Fix: Use `require('rx-lite')` for Node.js environments. For browser usage, include `rx.lite.js` via a `<script>` tag, which exposes `Rx` globally.
breaking In versions prior to 4.0.6, `Rx.Observable.fromPromise(promise)` was known to swallow errors originating from Observable instances within the promise chain, leading to silent failures.
Fix: Upgrade to `rx-lite` version 4.0.6 or newer. If upgrading is not possible, ensure robust error handling within your promises before converting them to Observables.
deprecated The package name `rx-lite` is an artifact of RxJS v4. Modern RxJS uses the package name `rxjs` and does not differentiate between 'lite' and 'core' versions in the same way, as it is tree-shakable by default.
Fix: Use `npm install rxjs` for new projects or when migrating. Consult the official RxJS documentation for current best practices.

Install

npm install rx-lite npm
yarn add rx-lite yarn
pnpm add rx-lite pnpm

Imports

Rx
wrong:
```
import Rx from 'rx-lite';
```
correct:
```
const Rx = require('rx-lite');
```
RxJS v4 is a CommonJS module for Node.js. ESM import syntax is not supported and will fail.

Observable

wrong:

import { Observable } from 'rx-lite';

correct:

const Rx = require('rx-lite');
const Observable = Rx.Observable;

Observable is a property of the global 'Rx' object, not a named export.

fromPromise

wrong:

import { fromPromise } from 'rx-lite';

correct:

const Rx = require('rx-lite');
const myObservable = Rx.Observable.fromPromise(somePromise);

Operators are attached to Rx.Observable. Named ESM imports are not available in this version.

Quickstart

Demonstrates creating an observable from an array, applying map and filter operators, and subscribing to log values. Also shows converting a Promise to an Observable.

const Rx = require('rx-lite');

const source = Rx.Observable.fromArray([1, 2, 3, 4, 5]);

const subscription = source
  .map(x => x * 2)
  .filter(x => x > 5)
  .subscribe(
    x => console.log('Next: ' + x),
    err => console.error('Error: ' + err),
    () => console.log('Completed')
  );

// Example with a promise
const somePromise = Promise.resolve('Hello from Promise!');
Rx.Observable.fromPromise(somePromise)
  .subscribe(
    data => console.log('Promise data: ' + data),
    err => console.error('Promise error: ' + err)
  );

// To stop listening (important for long-lived observables)
// subscription.dispose();

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