code advice on buzz()

But when the handle is lost the timeout never gets cleared, because there is no handle to it.

This is really not the case... x is just a number, clearing the variable has no effect to clearTimeout since a timeout from setTimeout only runs ONCE. Try it...

• Do reset() on your Bangle to ensure there's nothing running in the background
  
• Run global["\xff"].timers - this lets you see the internal list of timers, and it should be []
  
• Run var x then if (x) clearTimeout(x);x = setTimeout(function() { x=undefined; print("Hello") }, 60000)
  
• Run global["\xff"].timers again - you'll see a timer
  
• Wait 1 minute for the timer to execute and 'Hello' to be written
  
• Run global["\xff"].timers and you'll see there are no longer timers
  
  

Shouldn't this be done by clearTimeout?

Maybe in an ideal world, but it's just the way JS works. Try it on a desktop PC. setTimeout returns an integer, and that integer is never cleared.

I've tried to give you code that works above, what you suggest is broken for the reasons I already said.

Perhaps the issue is something else? You can verify it works - just upload this code:

var chimeTimer;

function planChime() {
  if (chimeTimer)
    clearTimeout(chimeTimer);
  chimeTimer = setTimeout(function() {
    chimeTimer = undefined;
    console.log("Buzz");
    Bangle.buzz().then(() => {
      console.log("Buzz done");
      setTimeout(function(){
         planChime();
      }, 2000);
    });
  }, 60000 - (Date.now() % 60000));
}

planChime();

It'll chime every minute. Now keep calling global["\xff"].timers - you'll see there is only ever one timer active at a time, which is the one for the next minute.

What did change a few months ago was how Bangle.buzz works - but the changes there were precisely to stop things like this from happening - it now uses a hardware timer, so people calling clearTimeout() can't accidentally stop the promise from working.