A Simple EventEmitter Implemented by JavaScript (ES6)

EventEmitter.js

class EventEmitter
{
    constructor()
    {
        this._listeners = new Map();
    }

    addListener(p_eventName, p_listener)
    {
        if (p_listener && typeof p_listener === "function")
        {
            if (this._listeners.has(p_eventName))
            {
                this._listeners.get(p_eventName).push(p_listener);
            }
            else
            {
                this._listeners.set(p_eventName, [p_listener]);
            }
            return true;
        }
        return false;
    }

    removeListener(p_eventName, p_listener)
    {
        if (this._listeners.has(p_eventName))
        {
            const listeners = this._listeners.get(p_eventName);
            const index = listeners.lastIndexOf(p_listener);
            if (index !== -1)
            {
                listeners.splice(index, 1);
                if (listeners.length === 0)
                {
                    this._listeners.delete(p_eventName);
                }
                return true;
            }
        }
        return false;
    }

    emit(p_eventName, ...p_args)
    {
        if (this._listeners.has(p_eventName))
        {
            this._listeners.get(p_eventName).forEach((l) => l(...p_args));
            return true;
        }
        return false;
    }

    on(p_eventName, p_eventHandler)
    {
        this.addListener(p_eventName, p_eventHandler);
    }

    off(p_eventName, p_eventHandler)
    {
        this.removeListener(p_eventName, p_eventHandler);
    }
}

const ee = new EventEmitter();

ee.on("click", (e) =>
{
    console.log("event data:", e);
});

ee.on("touch", (e) =>
{
    console.log("event data:", e);
});

ee.emit("click", {
    "A": "Jack"
});

ee.emit("touch", [1, 2, 3]);