How to use the isomorphic-ws.CLOSING function in isomorphic-ws

break;
      case WebSocket.CLOSED:
        // nothing to be done
        break;
      case WebSocket.CONNECTING:
        // imitate missing abort API
        this.socket.onopen = () => 0;
        this.socket.onclose = () => 0;
        this.socket.onerror = () => 0;
        this.socket.onmessage = () => 0;
        this.socket = undefined;
        if (this.closeHandler) {
          this.closeHandler({ wasClean: false, code: 4001 });
        }
        break;
      case WebSocket.CLOSING:
        // already closing. Let it proceed
        break;
      default:
        throw new Error(`Unknown readyState: ${this.socket.readyState}`);
    }
  }

ws.onclose = () => {
        if (ws && ws.readyState !== WebSocket.CLOSED && ws.readyState !== WebSocket.CLOSING) {
          ws.close();
        }
        if (ws.reconcileTimer) {
          clearInterval(ws.reconcileTimer);
          ws.reconcileTimer = null;
        }
        if (this.ws === ws) {
          this.ws = null;
          if (Object.keys(this.messageIdToSubscription).length) {
            this.initSocket();
          }
        }
      };