It seems I don't fully understand promises 😄 If the catch function doesn't explicitly return a value the then function shouldn't run, right? It looks you're seeing something different and I don't understand promises.

Here's the documentation I can find on catch()

The Promise returned by catch() is rejected if onRejected throws an error or returns a Promise which is itself rejected; otherwise, it is fulfilled.

I infer from this that if the function provided in catch() returns nothing, catch() itself returns a Promise that is fulfilled, hence the .then() is invoked. That matches what I see in my testing.

Alternatives to the fix I proposed could be:

• throwing an error in the catch() function
• explicitly returning a rejected Promise (e.g. the original Promise)

I've tested these, and both work - specifically:

either adding this line at the end of the catch() function

throw 'need to show permissions dialog';

or (more convoluted, and I think potentially rather confusing, but it does seem to work)....

const promiseRef = DeviceOrientationEvent.requestPermission().catch(function () {

and then at the end of the catch() function:

return promiseRef

Thanks for the explanation!