src/ol/events.js
function getListenerMap(target, opt_create) {
  let listenerMap = target.ol_lm;
  if (!listenerMap && opt_create) {
    listenerMap = target.ol_lm = {};
  }
  return listenerMap;
}
function getListenerMap(target, opt_create) {
  let listenerMap = target.ol_lm;
  if (!listenerMap && opt_create) {
    listenerMap = target.ol_lm = {};
  }
  return listenerMap;
}
function getListenerMap ( target , opt_create ) { let listenerMap = target . ol_lm ; if ( ! listenerMap && opt_create ) { listenerMap = target . ol_lm = { } ; } return listenerMap ; }
Get the lookup of listeners.
@param {Object} target Target.
@param {boolean=} opt_create If a map should be created if it doesn't exist.
@return {!Object<string, Array<EventsKey>>} Map of
listeners by event type.
Get the lookup of listeners .