evt
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    1.10.1 • Public • Published

    💧EventEmitter's typesafe replacement💧

    Home - Documentation - v2.0 🚀


    '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 browsers, react-native ...)

    • It is both a Deno and an NPM module. ( Achieved with Denoify )
    • Lightweight, no dependency.
    • No polyfills needed, the NPM module is transpiled down to ES3
    • React Hooks integration

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

    TL;DR*

    import { Evt } from "evt";
    
    const evtText = new Evt<string>();
    const evtTime = new Evt<number>();
    
    evtText.attach(text => console.log(text));
    evtTime.attachOnce(time => console.log(time));
    
    evtText.post("hi!"); //Prints "hi!"
    evtTime.post(123);   //Prints "123"
    evtTime.post(1234);  //Prints nothing

    OR

    import { Evt, to } from "evt";
    
    const evt = new Evt<
        [ "text",  string ] | 
        [ "time",  number ]
    >();
    
    //Mind the '$' prefixing 'attach'
    evt.$attach(to("text"), text => console.log(text));
    evt.$attachOnce(to("time"), time => console.log(time));
    
    evt.post(["text", "hi!"]);
    evt.post(["time", 123]);
    evt.post(["time", 1234]);

    in React, it let you attach event listeners without having to worry about detaching them.

    import { useState } from "react";
    import { Evt } from "evt";
    import { useEvt } from "evt/hooks";
    
    const evtTick = Evt.create();
    
    setInterval(()=> evtTick.post(), 1000);
    
    function App(){
    
        const [count, setCount]= useState(0);
    
        useEvt(ctx=> {
        
            evtTick.attach(ctx, ()=> setCount(count+1));
        
        },[count]);
        
        return <h1>tick count: {count}</h1>;
    
    
    }

    run it

    *Those are introductory examples, EVT can do much more than this.

    Who is using it


    Install / Import

    In Deno:

    import { Evt } from "https://deno.land/x/evt/mod.ts";

    Anywhere else:

    $ npm install --save evt
    import { Evt } from "evt"; 

    Import from HTML, with CDN

    <script src="//unpkg.com/evt/bundle.min.js"></script>
    <script>
        const { Evt } = window["evt"];
    </script>

    Try it

    Run some examples

    Motivations

    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.
    • With RxJS It is often needed to resort to custom type guards, the filter operator breaks the type inference.
    • RxJS tends to be quite verbose.
    • It could be months before RxJS it eventually supports Deno.
    • No official guideline on how to integrate RxJS with React.

    EVT is an attempt to address all these points while trying to remain as accessible as EventEmitter.

    Get started

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    Install

    npm i evt

    Homepage

    evt.land

    DownloadsWeekly Downloads

    4,471

    Version

    1.10.1

    License

    MIT

    Unpacked Size

    2.58 MB

    Total Files

    420

    Last publish

    Collaborators

    • xananax
    • garronej