A singleton class to manage events (pus-sub)

SingletonEvent.js

// A singleton class to manage events (pus-sub)

let eventManagerInstance = null;

export default class Event {

    constructor(){
        if (!stateManagerInstance) {
            stateManagerInstance = this;
            this.events = {};
        }
        return eventManagerInstance;
    }

    on(eventName, fn) {
        this.events[eventName] = this.events[eventName] || [];
        this.events[eventName].push(fn);
    }

    off(eventName, fn) {
        if (this.events[eventName]) {
            for (var i = 0; i < this.events[eventName].length; i++) {
                if (this.events[eventName][i] === fn) {
                    this.events[eventName].splice(i, 1);
                    break;
                }
            };
        }
    }

    trigger(eventName, data) {
        if (this.events[eventName]) {
            this.events[eventName].forEach(function(fn) {
                fn(data);
            });
        }
    }

}