Timers that cannot outlive the app that started them.
Residency is what makes this more than tidiness. An app stays mounted after you leave
it and is unmounted later, without warning, when it falls off the end of
MAX_RESIDENT_APPS — so a bare setTimeout can fire against a torn-down component
tree, and the callback writes to state nothing is rendering any more. Three sites had
no stored handle at all and could not have been cleaned up even deliberately.
onAppUnmount clears whatever is still pending. Note the argument order is
duration-first — after(600, fn) reads as the sentence it is — which is the
opposite of setTimeout.
Timers that cannot outlive the app that started them.
Residency is what makes this more than tidiness. An app stays mounted after you leave it and is unmounted later, without warning, when it falls off the end of
MAX_RESIDENT_APPS— so a baresetTimeoutcan fire against a torn-down component tree, and the callback writes to state nothing is rendering any more. Three sites had no stored handle at all and could not have been cleaned up even deliberately.onAppUnmountclears whatever is still pending. Note the argument order is duration-first —after(600, fn)reads as the sentence it is — which is the opposite ofsetTimeout.