> ## Documentation Index
> Fetch the complete documentation index at: https://developer.suki.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Form Filling SDK Event Handling

> Learn how to subscribe to FormFillingClient emitter events for analytics, logging, and persistent handlers using the Form filling SDK

This example shows how to subscribe to Form filling SDK events with `client.on()`. You register listeners once when you create `FormFillingClient`, then use them for analytics, logging, or saving background results across every session on the page.

Callbacks such as `onSubmit` run for one session at a time. Event listeners stay active until you unsubscribe. Refer to [Events](/form-filling-sdk/api-reference/events) for when each event fires.

```javascript JavaScript theme={"theme":{"light":"github-dark","dark":"material-theme-darker"}}
import { FormFillingClient, SukiFormFillingError } from "@suki-sdk/form-filling";

const client = new FormFillingClient({ authManager });

const unsubscribers = [
  client.on("form-filling:ready", () => {
    analytics.track("form_filling_ready");
  }),
  client.on("form-filling:session-started", (payload) => {
    analytics.track("form_filling_session_started", {
      ambient_session_id: payload.ambient_session_id,
      correlation_id: payload.correlation_id,
    });
  }),
  client.on("form-filling:submitted", (result) => {
    analytics.track("form_filling_submitted", {
      ambient_session_id: result.ambient_session_id,
      form_count: result.structured_data.generated_values.length,
    });
  }),
  client.on("form-filling:background-submitted", (result) => {
    persistToBackend(result);
  }),
  client.on("form-filling:error", (err) => {
    if (err instanceof SukiFormFillingError) {
      analytics.track("form_filling_error", { code: err.code, reason: err.reason });
    }
  }),
];

// On app teardown:
// unsubscribers.forEach((off) => off());
```

<Note>
  `form-filling:submitted` removes the iframe for a foreground session. `form-filling:background-submitted` does not: it means results arrived for a session that is no longer the foreground session (for example after replace or reopen), not merely that processing took longer than 60 seconds.
</Note>

## Next steps

<Icon icon="file-lines" iconType="solid" /> Refer to [Events](/form-filling-sdk/api-reference/events) for all event names and lifecycle

<Icon icon="file-lines" iconType="solid" /> Refer to [Webhook handler](/form-filling-sdk/examples/webhook-handler) for server-side saves

<Icon icon="file-lines" iconType="solid" /> Refer to [EHR handoff](/form-filling-sdk/examples/ehr-handoff) to map `structured_data` to your EHR