onReady fires once when an element has finished mounting and is ready for shopper interaction. Use it to flip a loading skeleton off, focus an input, or kick off follow-up element creation.
Payload
Example
One-shot signal
onReady fires exactly once per element instance. It does not fire again after update(), remount, or theme changes. If you re-mount an element, subscribe again on the new handle.
Do not gate mount() on onReady; mount() is itself the trigger. Subscribe before calling mount() so the event is not missed.
Wallet elements
ForapplePay and googlePay, onReady is deferred until the device-availability probe resolves. On an unavailable device, onReady never fires and onChange fires with { available: false, reason } instead.
onChange (which fires regardless) when you need a signal that fires on every device, including unavailable ones.