How to use the eventsource.CLOSED function in eventsource

eventSource.addEventListener("error", (e: any) => { // eslint-disable-line @typescript-eslint/no-explicit-any
        if (e.status) { // If the error has an HTTP status code associated with it...
          eventSource.close()
          reject(new Error(`Received ${e.status} from the API server when attempting to open job "${this.name}" log stream`))
        } else if (eventSource.readyState == EventSource.CONNECTING) {
          // We lost the connection and we're reconnecting... nbd
          this.logger.debug("Reconnecting to log stream")
        } else if (eventSource.readyState == EventSource.CLOSED) {
          // We disconnected for some unknown reason... and presumably exhausted
          // attempts to reconnect
          reject(new Error(`Encountered unknown error receiving job "${this.name}" log stream`))
        }
      })
      eventSource.addEventListener("done", () => {

setTimeout(function () {
      if (es.readyState === EventSource.CLOSED) {
        that.emit('error', err);
        that.close(true);
      }
    }, 100);
  };

source.addEventListener('error', e => {
  if (e.readyState === EventSource.CLOSED) {
    console.log('Connection was closed! ', e);
  } else {
    console.log('An unknown error occurred: ', e);
  }
}, false);