Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The registration read-only property of the SyncEvent interface returns a reference to a SyncRegistration object.
Syntax
var syncReg = SyncEvent.registration
Value
A SyncRegistration object