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utilities: keep a single pending watch callback - #74
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watch() defers the callback with setTimeout on every effect run, but remembered only the last timer. When the effect ran more than once before the timers fired, e.g. after a change made in the same tick as an immediate watch was created, every timer called the callback, and all of them read the same latest value: the first reported the change, the rest reported it again with the old value equal to the new one. The disposer cancelled only the last timer, so the earlier ones still fired after disposal. Cancel the pending timer before setting a new one. The callback now runs once with the latest value, and disposal cancels it.
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watch()set a newsetTimeouton every effect run but remembered only the last one. When the effect ran more than once before the timers fired, for example after a change made in the same tick as an immediate watcher was created, the callback ran once per timer: the extra calls repeated the latest value with the old value equal to the new one. Disposal cancelled only the last timer, so the earlier ones still fired after it.Cancel the pending timer before setting a new one, so the callback runs once with the latest value and disposal cancels it. This affects the one-way
x-boundbindings (.inand.out) andx-router.