const events = (function() {
    const events = {};

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

        off(eventName, fn) {
            const currentEvents = events[eventName];

            if (!currentEvents || !currentEvents.length) {
                return;
            }

            const index = currentEvents.indexOf(fn);

            if (index > -1) {
                currentEvents.splice(index, 1);
            }
        },

        emit(eventName, data) {
            (events[eventName] || []).forEach(fn => fn(data));
        },
    };
})();