var torchRunning = false;
var startTime = new Date();

function sleep(milliseconds) { // A basic sleep implementation to "pause" the current thread
  var start = new Date().getTime();
  for (var i = 0; i < 1e7; i++) {
    if ((new Date().getTime() - start) > milliseconds){
      break;
    }
  }
}

function switchLight() {
  torchRunning = !torchRunning;
  console.log(torchRunning);
}

// One light pulsation (ON -> OFF) per 20 ms (10 ms -> ON , 20 ms -> OFF)
for(let i = 0; i < 100; i++) // 100 switchLight() -> 50 pulsations
{
  sleep(10);
  switchLight();
}

var endTime = new Date();
var elapsed = (endTime - startTime) / 1000; // Should be -> 20 x 50 = 1000 ms
console.log(elapsed);

// => After running this script ten times, here are the results :
/*
  1.103
  1.102
  1.118
  1.105
  1.103
  1.107
  1.112
  1.108
  1.103
  1.112

*/


function isValid(time) { // Ensures 1 second has elapsed
  return time == 1;
}

console.log( isValid(elapsed) ? 'Okay, all good':'Wrong :( ' );

// => Wrong :( ten times