ws.onmessage = function(event) {
                    var messages = document.getElementById('messages')
                    var message = document.createElement('li')
                    var content = document.createTextNode(event.data)
                    message.appendChild(content)
                    messages.appendChild(message)
                };
                event.preventDefault()
            }

                ws.onmessage = function(event) {
                    var messages = document.getElementById('messages')
                    var message = document.createElement('li')
                    var content = document.createTextNode(event.data)
                    message.appendChild(content)
                    messages.appendChild(message)
                };
                event.preventDefault()
            }

                throwValidationError(messages -> messages.addErrorsCrudFailedToCreateCrudTable(GLOBAL, buildThrowableMessage(e)),
                        this::asEditHtml);
            }
        }).orElse(() -> {
            throwValidationError(messages -> messages.addErrorsCrudFailedToCreateInstance(GLOBAL), this::asEditHtml);
        });
        return redirect(getClass());
    }

    /**

   * messages.
   */
  open fun onOpen(
    webSocket: WebSocket,
    response: Response,
  ) {
  }

  /** Invoked when a text (type `0x1`) message has been received. */
  open fun onMessage(
    webSocket: WebSocket,
    text: String,
  ) {
  }

  /** Invoked when a binary (type `0x2`) message has been received. */
  open fun onMessage(

                ws.onmessage = function(event) {
                    var messages = document.getElementById('messages')
                    var message = document.createElement('li')
                    var content = document.createTextNode(event.data)
                    message.appendChild(content)
                    messages.appendChild(message)
                };
                event.preventDefault()
            }

**FastAPI** provides the same `WebSocket` directly just as a convenience for you, the developer. But it comes directly from Starlette.

///

## Await for messages and send messages { #await-for-messages-and-send-messages }

In your WebSocket route you can `await` for messages and send messages.

{* ../../docs_src/websockets/tutorial001_py39.py hl[48:52] *}

You can receive and send binary, text, and JSON data.

## Try it { #try-it }

                logger.warn("Failed to print a thread dump.", e);
                throwValidationError(messages -> messages.addErrorsFailedToPrintThreadDump(GLOBAL), this::asListHtml);
            }
        }).orElse(() -> {
            throwValidationError(messages -> messages.addErrorsCrudCouldNotFindCrudTable(GLOBAL, id), this::asListHtml);
        });
        return redirect(getClass());
    }

)

var (
	auditFailedMessagesMD = NewCounterMD(auditFailedMessages,
		"Total number of messages that failed to send since start",
		targetID)
	auditTargetQueueLengthMD = NewGaugeMD(auditTargetQueueLength,
		"Number of unsent messages in queue for target",
		targetID)
	auditTotalMessagesMD = NewCounterMD(auditTotalMessages,
		"Total number of messages sent since start",
		targetID)
)

// loadAuditMetrics - `MetricsLoaderFn` for audit

        </form>
        <ul id='messages'>
        </ul>
        <script>
            var client_id = Date.now()
            document.querySelector("#ws-id").textContent = client_id;
            var ws = new WebSocket(`ws://localhost:8000/ws/${client_id}`);
            ws.onmessage = function(event) {
                var messages = document.getElementById('messages')
                var message = document.createElement('li')

        assertTrue(ts.contains(ex.getMessage()), "toString should contain the detail message");
    }

    @ParameterizedTest(name = "Message preserved: [{0}]")
    @MethodSource("messages")
    @DisplayName("Message constructor preserves provided messages, including null/edge cases")
    void messageConstructor_preservesMessage(String msg) {
        // Arrange & Act