Are promises blocking?

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  • I have a simple blinking light in the background on my NRF52840 board. It blinks every like 1 second. But when i'm waiting for one of my promises to resolve the blinking light seems to be not working.

    So do promises block the thread?

  • It actually might be the fact that my task is running a little longer then i first thought. So i'm guessing until my main task is finished or is halted by a promises. A set timeout won't trigger?

  • Also sorry for my bad terminology. I don't actually know how to describe of Environment. Its like a light multitasking environment. Javascript as a "operating system".

  • Your terminology sounds fine to me! A promise chain itself is not blocking but in JavaScript the execution of function code is (unless you declare it 'async' which Espruino doesn't support - but all that does it effectively split the function into a bunch of smaller sync functions joined with promises).

    So Espruino can only run one bit of code at a time (it's not pre-emptive), but by splitting the code up and calling the next bit of code from a promise/callback it can then interleave those smaller bits of code and make it seem multi-tasking.

    So in your case as you noted I think maybe one part of the promise is just taking a long time to finish?

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Are promises blocking?

Posted by Avatar for user156811 @user156811