> For the complete documentation index, see [llms.txt](https://docs.evt.land/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.evt.land/v1/readme.md).

# Why EVT ?

![](https://github.com/garronej/evt/workflows/ci/badge.svg?branch=develop) ![](https://img.shields.io/bundlephobia/minzip/evt) ![](https://img.shields.io/npm/dw/evt) ![](https://img.shields.io/npm/l/evt)

`'evt'` is intended to be a replacement for `'events'`.\
It enables and encourages **functional programming** and makes heavy use of **typescript**'s type inference features to provide **type safety** while keeping things **concise and elegant** 🍸.

**Suitable for any JS runtime env (deno, node, old browser, react-native ...)**

* ✅  It is both a [Deno](https://deno.land/x/evt) and an [NPM](https://www.npmjs.com/evt) module. 
* ✅  Lightweight, no dependency.
* ✅  No polyfills needed, the NPM module is transpiled down to ES3.
* ✅  [React Hooks integration](https://docs.evt.land/api/react-hooks)

Can be imported in TypeScript projects using version >= **3.4** (Mar 2019) and in any plain JS projects.

## Motivation

There are a lot of things that can't easily be done with `EventEmitter`:

* Enforcing **type safety**.
* Removing a particular listener ( if the callback is an anonymous function ).
* Adding a one-time listener for the next event that meets a condition.
* Waiting (via a Promise) for one thing or another to happen.

  *Example: waiting at most one second for the next message, stop waiting if the socket disconnects.*

Why would someone pick EVT over RxJS:

* RxJS introduces a lot of abstractions. It's a big jump from `EventEmitter`.
* It is often needed to resort to custom [type guards](https://www.typescriptlang.org/docs/handbook/advanced-types.html#user-defined-type-guards), the filter operator [breaks the type inference.](https://stackblitz.com/edit/evt-795plc?embed=1\&file=index.ts\&hideExplorer=1)
* Tend to be quite verbose.
* It could be months before it eventually supports Deno.
* There is no official guideline on how to integrate it with React.

EVT is an attempt to build a lib as accessible as the `EventEmitter` yet much more powerfull.


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