JSEmitter

Lightweight Event Emitter class written in typescript that works on both client and server with no dependencies

Usage

The event emitter can be used with both vanilla js and typescript

Typescript Example

import {JSEmitter} from "jsemitter";

class Clock extends JSEmitter {
    constructor() {
        super();
        (<any>window).setInterval(this.tickTock, 1000);
    }

    private tickTock(): void {
        this.emit('onTick', new Date())
    }
}

let clock = new Clock();

// subscribe to the onTick Event
clock.on('onTick', (theDate) => {
    console.log(`The time is ${theDate}`);
    this.count++;
    if (this.count > 10) {
        // unsubscribe after 10 seconds
        clock.off('onTick');
        console.log('Clock stopped after 10 seconds');
    }
});

Methods

on

Fires a callback when an event is emitted that matches the key

Function Signature

on(key, callback)

Example

on('something-happened', (data)=>{
    // event fired 
    // do something with the data
})

once

Fires a callback one time when an event is emitted that matches the key. After the event is is fired the callback is removed and will not fire again

Function Signature

once(key, callback)

Example

once('something-happened', (data)=>{
    // event fired 
    // do something with the data, it won't be fired again
})

many

Fires a callback a specific number of times time when an event is emitted that matches the key. After the event is is fired the callback is removed and will not fire again

Function Signature

once(key, callback, count)

Example

once('something-happened', (data)=>{
    // This event will fire 7 times and then be removed
}, 7)

emit

Sends an event to any callback listening to the key

Function Signature

emit(key, data)

Example

emit('something-happened', 'Hello');
emit('something-else', {someObject:true});

off

Removes a specific callback associated with the key

Function Signature

off(key, callback)

Example

off('something-happened', (data)=>{})

offAll

Removes all callbacks attached to the event emitter

Function Signature

offAll()

Example

offAll()

offKey

Removes a callback associated with the key

Function Signature

offKey(key)

Example

off('something-happened')