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JSR Score
64%
Published
4 weeks ago (3.1.0)

evtemitter

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Total alerts Language grade: JavaScript Deno

A typed Eventemitter for Deno and the browser.

This EventEmitter is based on CustomEvents fully compatible with the standard EventTarget, which means, you can use addEventListener, removeEventListener and dispatchEvent exactly as you are used to, and allows strong typing of events as well as reserved events that can only be invoked from an extending class.

There are different ways to use this EventEmitter:

  • You can use it without typed events, like an untyped EventEmitter:

    // JSR
    import { EventEmitter } from "@apollo79/evtemitter";
    // or alternatively https://deno.land/x/
    // import { EventEmitter } from "https://deno.land/x/evtemitter@2.0.0/mod.ts";
    
    const target = new EventEmitter();
    
    target.on("foo", (detail) => {
      console.log(detail); // undefined
    });
    
    target.emit("foo");
    
    target.on("bar", (detail) => {
      console.log(detail); // hello world
    });
    
    target.emit("bar", "hello world");
    
  • You can use it as typed EventEmitter that provides strongly typed events and methods with autocompletion in you code editor.

    import { EventEmitter } from "https://deno.land/x/evtemitter@2.0.0/mod.ts";
    
    type Events = {
      foo: undefined;
      bar: string;
    };
    
    const emitter = new EventEmitter<Events>();
    
    target.on("foo", (detail) => {
      console.log("Foo has been emitted");
    });
    
    // works
    target.emit("foo");
    
    // would throw an exception
    // target.emit("foo", "hello world");
    
    target.once("bar", (detail) => {
      console.log("Bar has been emitted");
    });
    
    // works
    target.emit("bar", "hello world");
    
    // would throw an exception
    // target.emit("bar", 123);
    
  • And you can use it with reserved events, which is for example useful if you want to allow everyone to emit message events but in your class you want to emit a connection event. Of course, this type of emitter is also strongly typed and provides autocompletion:

    import { EventEmitter } from "https://deno.land/x/evtemitter@2.0.0/mod.ts";
    
    // Events that can be emitted via `emit`, `dispatch` and `publish` and that can be listened to
    type UserEvents = {
        message: string;
    };
    
    // Events that can only be emitted via the protected `emitReserved` method. It is also possible to listen to these events
    type ReservedEvents = {
        connection: { name: string };
    };
    
    class Implementing extends EventEmitter<
        UserEvents
        ReservedEvents
    > {
        constructor() {
            super();
    
            // your logic here
        }
    
        onConnect(name: string) {
            // logic here...
            this.emitReserved("connection", { name });
        }
    }
    
    const target = new Implementing();
    
    target.addEventListener("connection", (event) => {
        const name = event.detail.name; // this is typed as a string in this example
    
        console.log(`${name} has connected!`);
    });
    
    // of course, this makes no sense in reality, it's just for showing
    target.onConnect("Apollo");
    
    target.pull("message").then((message) => {
        console.log(message);
    });
    
    target.emit("message", "hello world");
    
    // this would throw an exception
    // target.emit("connection", "Apollo");
    

Add Package

deno add @apollo79/evtemitter

Import symbol

import * as mod from "@apollo79/evtemitter";

Add Package

npx jsr add @apollo79/evtemitter

Import symbol

import * as mod from "@apollo79/evtemitter";

Add Package

yarn dlx jsr add @apollo79/evtemitter

Import symbol

import * as mod from "@apollo79/evtemitter";

Add Package

pnpm dlx jsr add @apollo79/evtemitter

Import symbol

import * as mod from "@apollo79/evtemitter";

Add Package

bunx jsr add @apollo79/evtemitter

Import symbol

import * as mod from "@apollo79/evtemitter";