AudioContext dies (silently) in IOS14 Safari on iPad

[nmcgann]

If the tab with the metronome app is made inactive the AudioContext is 'suspended' / 'interrupted' and has to be manually re-started with audioContext.resume(); in the play() function once the tab is made active again. (see https://developer.mozilla.org/en-US/docs/Web/API/BaseAudioContext/state)

This works on Chrome, but not in Safari. AudioContext is apparently re-started and running in Safari, but the audio clock is frozen leaving the application dead. The only workround I have found is to detect the 'suspended' or 'interrupted' state and then close the AudioContext and make a new one (plus any associated nodes like gain).

This then works in both Safari and Chrome. (see https://github.com/nmcgann/metronome for this fix and various other added features)