Basic addEventListener and removeEventListener, in case I need it later

eventlistener.js

var eventListeners = {
  eventName: []
};

function addEventListener(type, listener) {
  var listeners = eventListeners[type];
  if (listeners) {
    listeners.push(listener);
  }
}

function removeEventListener(type, listener) {
  var listeners = eventListeners[type];
  if (listeners) {
    let index = listeners.indexOf(listener);
    if (index > -1) {
      listeners.splice(index, 1);
    }
  }
}