Stopwatch

control multiple concurrent stopwatches

Features

• can start multiple stopwatches concurrently
• supports PWA
• stopwatches and increment are stored in localStorage
• shows error in real time when input is invalid

Display

• displayed time is updated synchonously, using a single setInterval()
• displayed time is calculated with Date.prototype.getTime()
  • so even if the computer is set to sleep or the phone's screen is off, a started stopwatch will still display time elapsed in real life

Input

• when paused, stopwatches are editable
  • e.g. change to 02:99:69 will set stopwatch to 03:40:09
  • e.g. change to 65536 will set stopwatch to 18:12:16 (i.e. 65536 seconds)
• new stopwatches can be added by entering a set of names (space sperated)
  • names should be distinct (to delete stopwatches at $\mathcal O(1)$ time)
  • use @ to specify initial duration (default is 0)
  • the reset button will reset stopwatch to its initial duration
  • e.g. enter a o e u will create stopwatches named "a", "o", "e", and "u"
  • e.g. enter q@900 w@00:15:00 will create stopwatches named "q" and "w" that starts at 00:15:00 as their initial duration
• increment can be changed
  • an increment of $n$ means for each second passed, $n$ seconds will be added to all stopwatches that are on
  • e.g. increment of -1 can be used as timer (i.e. countdown)
  • if increment is negative and stopwatch is at 00:00:00, the stopwatch will stay at 00:00:00 for the next second