Displaying deciseconds on timer app

[DanHuang]

Hello,

I'm trying to build a timer app that displays a count down timer like the in-built one. However I am quite stuck in making it display the deci-seconds (10th of seconds ). Is there a way to achieve this goal?

Thanks!

[JonFitbit · Accepted solution]

I'm not sure you'll get that level of granularity, but you can try something like:

1. use the display api to detect when the screen comes on

2. start a timer using setInterval()

3. update the display to show the time

import { display } from "display";

let intervalID; 

display.addEventListener("change", () => {
  if (display.on) {
    start();
  } else {
    stop();
  }
})

function start() {
  // display goes on 
  intervalID = setInterval(updateDisplay, 100); // 10ths second
}

function stop() {
  // display goes off 
  if(intervalID) { clearInterval(intervalID); }
}

function updateDisplay() {
let now = new Date();
let ms = now.getMilliseconds();
// set appropriate image href
}