in lib/event_handler.js [64:78]
off(eventName, callback) {
const handlers = this.eventHandlers[eventName] || [];
if (callback) {
const index = handlers.indexOf(callback);
if (index === -1) {
throw new Error(
`Could not turn off specified event listener for "${eventName}": not found as a listener`,
);
}
handlers.splice(index, 1);
} else {
delete this.eventHandlers[eventName];
}
return true;
}