# observable-fns
> Light-weight observable implementation and utils written in TypeScript. Based on zen-observable.
Latest version **0.6.1** (published 2021-05-30) · MIT license · 0 weekly downloads
## Install
```sh
npm install observable-fns
pnpm add observable-fns
yarn add observable-fns
bun add observable-fns
```
## Health
**Score 20/100 (F)** — status: abandoned.
Positive: esm support; no vulnerabilities.
Warnings: low downloads; no types; pre 1.0.
Negative: abandoned; low maintenance score.
## Facts
| | |
|---|---|
| Version | 0.6.1 |
| Published | 2021-05-30 |
| First published | 2019-12-08 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | none |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 97.7 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 50 |
| Author | Andy Wermke |
| Maintainers | andywer |
## Links
- npm: https://www.npmjs.com/package/observable-fns
- Repository: https://github.com/andywer/observable-fns
- Homepage: https://github.com/andywer/observable-fns#readme
- Issues: https://github.com/andywer/observable-fns/issues
- npm.io page: https://npm.io/package/observable-fns
## Recent versions
- 0.6.1 (latest) — 2021-05-30
- 0.5.1-test (testing) — 2020-02-15
- 0.6.0 — 2021-05-28
- 0.5.1 — 2020-02-20
- 0.5.0 — 2019-12-15
- 0.4.0 — 2019-12-08
## README
🕵️♀️ observable-fns
Light-weight Observable implementation and common toolbelt functions. Based on [`zen-observable`](https://github.com/zenparsing/zen-observable), re-implemented in TypeScript. Zero dependencies, [tree-shakeable](https://bitsofco.de/what-is-tree-shaking/).
The aim is to provide a lean Observable implementation with a small footprint that's fit to be used in libraries as an alternative to the huge RxJS.
Find all the provided functions and constructors in the 👉 [API Documentation](./docs/API.md)
🧩 Composable functional streams
🚀 map(), filter() & friends support async handlers
🔩 Based on popular [`zen-observable`](https://github.com/zenparsing/zen-observable), re-implemented in TypeScript
🌳 Zero dependencies, [tree-shakeable](https://bitsofco.de/what-is-tree-shaking/)
---
## Installation
```
npm install observable-fns
```
## Observable?
An observable is basically a stream of asynchronously emitted values that you can subscribe to. In a sense it is to the event emitter what the promise is to the callback.
The main difference to a promise is that a promise only resolves once, whereas observables can yield values repeatedly. They can also fail with an error, like a promise, and they come with a completion event to indicate that no more values will be send.
For a quick introduction on how to use observables, check out the [zen-observable readme](https://github.com/zenparsing/zen-observable).
```js
import { Observable, multicast } from "observable-fns"
function subscribeToServerSentEvents(url) {
// multicast() will make the observable "hot", so multiple
// subscribers will share the same event source
return multicast(new Observable(observer => {
const eventStream = new EventSource(url)
eventStream.addEventListener("message", message => observer.next(message))
eventStream.addEventListener("error", error => observer.error(error))
return () => eventStream.close()
}))
}
subscribeToServerSentEvents("http://localhost:3000/events")
.filter(event => !event.isStale)
.subscribe(event => console.log("Server sent event:", event))
```
## Usage
You can import everything you need directly from the package:
```js
import { Observable, flatMap } from "observable-fns"
```
If you write front-end code and care about bundle size, you can either depend on tree-shaking or explicitly import just the parts that you need:
```js
import Observable from "observable-fns/observable"
import flatMap from "observable-fns/flatMap"
```
Functions like `filter()`, `flatMap()`, `map()` accept asynchronous handlers – this can be a big win compared to the usual methods on `Observable.prototype` that only work with synchronous handlers.
Those functions will also make sure that the values are consistently emitted in the same order as the input observable emitted them.
```js
import { Observable, filter } from "observable-fns"
const existingGitHubUsersObservable = Observable.from(["andywer", "bcdef", "charlie"])
.pipe(
filter(async name => {
const response = await fetch(`https://github.com/${name}`)
return response.status === 200
})
)
```
## API
See [docs/API.md](./docs/API.md) for an overview of the full API.
## License
MIT
---
_Source: https://npm.io/package/observable-fns · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._