javascript - Start calling js function when PC wakeup from sleep mode

Question

In my aspx page, I use xmlhttp.response to update a part of this page. This update occurs in every 3 seconds using js function. But when my PC goes to sleep mode, this update doesn't happen. This is OK. But when PC wake up from sleep mode, I need to start update automatically without reload this page. How to do this?

Answer 1

You can detect disruptions in the JS timeline (e.g. laptop sleep, alert windows that block JS excecution, debugger statements that open the debugger) by comparing change in wall time to expected timer delay. For example:

var SAMPLE_RATE = 3000; // 3 seconds
var lastSample = Date.now();
function sample() {
  if (Date.now() - lastSample >= SAMPLE_RATE * 2) {
    // Code here will only run if the timer is delayed by more 2X the sample rate
    // (e.g. if the laptop sleeps for more than 3-6 seconds)
  }
  lastSample = Date.now();
  setTimeout(sample, SAMPLE_RATE);
}

sample();