demo · v136

Migration probe

A diagnostic page: probes for the removed method, probes for its replacement, calls the replacement if available, and shows what each returns. Useful as a pre-deploy check for sites that still ship the legacy call.

Probing both APIs…
HTMLFencedFrameElement on this browser—
.prototype.canLoadOpaqueURL (legacy)—
navigator.canLoadAdAuctionFencedFrame (replacement)—
result of replacement()—

the code

// Before:
if (HTMLFencedFrameElement.prototype.canLoadOpaqueURL.call(el, urn)) { /* ... */ }

// After (136+):
if (await navigator.canLoadAdAuctionFencedFrame(urn)) { /* ... */ }

why this angle

The sibling concept does the removal probe in isolation. This concept is the field-deploy checklist: legacy gone, replacement present, replacement actually callable. Three rows = one decision: ship or roll back.

see also