Resume, Preview, and Debug

Resume

The first save returns a resumeToken alongside the responseId (on the saved event and in state()). Persist the pair and pass it back later:

form.on("saved", ({ responseId, resumeToken }) =>
  localStorage.setItem("surface-resume", JSON.stringify({ responseId, resumeToken }))
);

// On a later visit:
const stored = JSON.parse(localStorage.getItem("surface-resume") ?? "null");
const form = await SurfaceForms.init({
  ...options,
  ...(stored && { resume: stored }),
});

Boot fetches the stored answers and seeds the engine: writes become updates (no duplicate response), earlier answers land in state().answers for prefilling, and stored meta.custom values carry forward.

A failed fetch (wrong token, deleted response) warns and starts a fresh session. The token proves the caller obtained the response ID legitimately; never build resume links from IDs alone. Resume is ignored in preview mode.

Preview mode

SurfaceForms.init({ ...options, preview: true, previewToken: "..." });

Blocks every network write: identify, responses, events, journey, enrichment, tracking. The scheduler books synthetically and email validation resolves synthetic valid verdicts, so the whole flow is walkable offline.

previewToken comes from the create_form or get_sdk_binding_map reply; with it, a never-published form serves its draft configuration.

Debug mode

SurfaceForms.init({ ...options, debug: true });

Development only. Logs every captured answer, lifecycle event, and navigation intent (a next requested from step ... line per call), audits answers against the record, and warns on states the server would reject and on inert configuration.

In production, two diagnostics remain: form.state() (current step, answers, responseId, finished) and form.capabilities ({ enrichment, emailValidation, tracking }).