js/90-timers.js

   1 let offset = 0;
   2
   3 function update_timer(timer){
   4         const start = parseInt(timer.dataset.start);
   5         const stop  = parseInt(timer.dataset.stop);
   6         const value = parseInt(timer.dataset.value);
   7         const now   = Math.floor(Date.now() / 1000) + offset;
   8
   9         const left = Math.max(stop - now, 0);
  10         const total = stop - start;
  11
  12         if(value)
  13                 timer.innerHTML = Math.floor(Math.max(value * 3 / 10, value * left / total));
  14         else {
  15                 let hours = Math.floor(left / 60 / 60);
  16                 hours = hours < 10 ? '0' + hours : hours;
  17                 let minutes = Math.floor(left / 60) % 60;
  18                 minutes = minutes < 10 ? '0' + minutes : minutes;
  19                 let seconds = left % 60;
  20                 seconds = seconds < 10 ? '0' + seconds : seconds;
  21                 timer.innerHTML = hours + ':' + minutes + ':' + seconds;
  22         }
  23 }
  24
  25 $(() => {
  26         $('.timer').each(item => {
  27                 update_timer(item);
  28                 setInterval(() => update_timer(item), 1000);
  29         });
  30         if($('.timer').length > 0) {
  31                 const xhr = new XMLHttpRequest();
  32                 xhr.open('HEAD', '/');
  33                 xhr.onload = () => {
  34                         const srvtime = Date.parse(xhr.getResponseHeader('Date'));
  35                         offset = Math.ceil((srvtime - Date.now()) / 1000);
  36                         console.log("Offset from server: " + offset);
  37                 };
  38                 xhr.send();
  39         }
  40 });