Polyfill fallback for ISO 8601 Week of Year and Year of Week calculations.
Introduced because highly experimental native browser implementations of the Temporal API
(e.g., Chrome/Firefox behind flags) currently return undefined for weekOfYear and yearOfWeek
on ZonedDateTime objects. The TC39 spec moved toward calendar-dependent definitions,
causing divergence between the @js-temporal/polyfill (which returns numbers) and native browsers (which return undefined).
Parameters
zdt: input
The ZonedDateTime or matching input object
Returns result
An object containing the weekOfYear and yearOfWeek
Polyfill fallback for ISO 8601 Week of Year and Year of Week calculations.
Introduced because highly experimental native browser implementations of the Temporal API (e.g., Chrome/Firefox behind flags) currently return
undefinedforweekOfYearandyearOfWeekon ZonedDateTime objects. The TC39 spec moved toward calendar-dependent definitions, causing divergence between the @js-temporal/polyfill (which returns numbers) and native browsers (which return undefined).