Simple event dispatcher implementation using JavaScript

dispatcher.js

export class Dispatcher {
    constructor () {
        this.events = {};   
    }
    
    addListener (event, callback) {
        // Check if the callback is not a function
        if (typeof callback !== 'function') {
            console.error(`The listener callback must be a function, the given type is ${typeof callback}`);
            return false;
        }
        
        
        // Check if the event is not a string
        if (typeof event !== 'string') {
            console.error(`The event name must be a string, the given type is ${typeof event}`);
            return false;
        }
        
        // Check if this event not exists
        if (this.events[event] === undefined) {
            this.events[event] = {
                listeners: []
            }
        }
        
        this.events[event].listeners.push(callback);
    }
    
    removeListener (event, callback) {
        // Check if this event not exists
        if (this.events[event] === undefined) {
            console.error(`This event: ${event} does not exist`);
            return false;
        }
        
    	this.events[event].listeners = this.events[event].listeners.filter(listener => {
    	    return listener.toString() !== callback.toString(); 
    	});
    }
    
    dispatch (event, details) {
        // Check if this event not exists
        if (this.events[event] === undefined) {
            console.error(`This event: ${event} does not exist`);
            return false;
        }
        
        this.events[event].listeners.forEach((listener) => {
            listener(details);
        });
    }  
}

// Example:
const dispatcher = new Dispatcher();

dispatcher.addListener('getUserInfo', (details) => {
    console.log(details);
});

dispatcher.dispatch('getUserInfo', {
    username: 'John',
    accountType: 'admin'
});