Preview player navigation

Scorm2004API.previewNavigationRequest("continue" | "previous") lets a host player check navigation before terminating the current SCO. This extension does not change the SCORM adl.nav.request_valid contract: a valid Continue request can still reach a blocked activity after End Attempt.

const preview = api.previewNavigationRequest("continue");
if (preview.outcome === "blocked") {
   showNavigationNotice(preview.exception);
   // Keep the current SCO document and runtime session alive.
   return;
}
api.SetValue("adl.nav.request", "continue");
api.Terminate("");

The synchronous result has these fields:

Field	Meaning
outcome	allowed, blocked, or unknown
targetActivityId	Predicted delivered activity ID, or null
endSequencingSession	Whether the request would end the sequencing session
exception	Sequencing diagnostic for a blocked result, or null

The preview runs normal termination, objective transfer, rollup and sequencing against an isolated copy of current tracking state. It includes CMI values already reported by the SCO and distinguishes content writes from LMS launch seeding. It does not terminate the live API, change attempts or bookmarks, emit host sequencing events, commit data, save persistence, or unload/deliver content. Genuine completion at the end of the course and authored Retry rules remain allowed.

Use the result immediately, then check again on a later click: subsequent CMI writes, elapsed time or changed objectives can change the outcome. It cannot predict future values that content has not yet reported. Time/elapsed-time providers must remain read-only, as they are during ordinary rule evaluation.

unknown means prediction is unavailable, not that navigation is prohibited. This includes an uninitialized/terminated runtime, missing/inactive sequencing, delivery in progress, custom model objects/accessors/callbacks that cannot safely be copied, and trees configured for random selection or randomization. No random draw is consumed. Hosts can retain ordinary navigation for unknown; such cases can still be refused after termination. Do not use this method to override a SCO's own Terminate request.