my event listener

function EventEmitter() {
  this._listenersObj = {};
}



EventEmitter.prototype.emit  = function (event) {
    const listeners = this._listenersObj[event];
    if(listeners) {
      listeners.forEach((listener) => {
        console.log('emit event', event);
        listener();
      });
    }
  }
EventEmitter.prototype.on = function(event, listener) {
  let x = this._listenersObj[event];
  this._listenersObj[event] = Array.isArray(this._listenersObj[event]) ? [...this._listenersObj[event], listener] : [listener];
}

EventEmitter.prototype.off = function(event, listener) {
  const x = this._listenersObj[event];
  if(x) {
    const listenerIndexToRemove = x.indexOf(listener);
    if(listenerIndexToRemove !== 1) {
      x.splice(listenerIndexToRemove, 1);
    }
    if(x.length === 0) {
      delete this._listenersObj[event];
    }
  }
  console.log('listener was removed',  this._listenersObj);
}

function listener() {
  console.log('listener was called')
}

const emitter = new EventEmitter();

emitter.on('dfg', listener);
emitter.emit('dfg');

emitter.off('dfg', listener);