• Dispatch a custom event.

    Note: this method is only supported in non-web environments due to usage of async_hooks to infer config.

    If you are using this method in the browser, please import and use from "@langchain/core/callbacks/dispatch/web".

    Parameters

    • eventName: string
    • payload: any

      The data for the custom event. Ideally should be JSON serializable to avoid serialization issues downstream, but not enforced.

    • Optionalconfig: RunnableConfig

      Optional config object.

    Returns Promise<void>

    import { dispatchCustomEvent } from "@langchain/core/callbacks/dispatch";

    const foo = RunnableLambda.from(async (input: string) => {
    await dispatchCustomEvent("my_custom_event", { arbitraryField: "someval" });
    return input;
    });

    const callbacks = [{
    handleCustomEvent: (eventName: string, payload: any) => {
    // Logs "my_custom_event" and { arbitraryField: "someval" }
    console.log(eventName, payload);
    }
    }];

    await foo.invoke("hi", { callbacks })
""