A signal that aborts when a or b does, carrying the reason of whichever
fired first (an already-aborted input aborts it at once).
Uses native AbortSignal.any when available; the fallback relay registers
listeners on both inputs, so call dispose() once the work using signal
has settled (always safe to call). With one input that input is returned
as is; with none the result is undefined (so a defined a always gives a
scope, which the return type says).
A signal that aborts when
aorbdoes, carrying the reason of whichever fired first (an already-aborted input aborts it at once).Uses native
AbortSignal.anywhen available; the fallback relay registers listeners on both inputs, so calldispose()once the work usingsignalhas settled (always safe to call). With one input that input is returned as is; with none the result isundefined(so a definedaalways gives a scope, which the return type says).