WhenMathTimer
Set a duration and start the countdown. This is a browser-local utility. It does not guarantee an audible alert, background execution, or a browser notification.
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Worked example
A 10-minute timer, checked again after exactly 3 minutes have passed, shows 7 minutes remaining, computed fresh from the actual target moment rather than an incrementing count that could drift. Pause that same timer right at the 3-minute mark, wait an untracked 20 minutes, then resume, and it still shows 7 minutes remaining at the moment of resuming, since the paused stretch never counted against the countdown.
Common mistakes
- Assuming the timer will make a sound or send a notification when it finishes. It only updates the on-screen display, and does not request notification permission or guarantee background execution on its own.
- Closing the tab and expecting the countdown to keep running. A closed tab stops the timer entirely, unlike a merely backgrounded one.
Limitations
If the tab is closed, the countdown stops immediately. A backgrounded but still open tab resumes with the correct remaining time once viewed again, since the remaining time is always recomputed from the real target moment rather than tracked separately.
Frequently asked questions
- Does refreshing the page keep the timer running?
- No, a refresh clears the timer completely, since this is a browser-local utility with no persisted state, not a background service that survives a page reload.
- What happens if the tab is backgrounded while the timer runs?
- Remaining time is always recomputed fresh from the actual target moment rather than incremented tick by tick, so returning to a backgrounded tab shows the correct remaining time immediately, with no drift accumulated while it was hidden.