script.js

console.clear();

function CountdownTracker(label, value) {
  var el = document.createElement('span');

  el.className = 'flip-clock__piece';
  el.innerHTML = '<b class="flip-clock__card card"><b class="card__top"></b><b class="card__bottom"></b><b class="card__back"><b class="card__bottom"></b></b></b>' + 
    '<span class="flip-clock__slot">' + label + '</span>';

  this.el = el;

  var top = el.querySelector('.card__top'),
      bottom = el.querySelector('.card__bottom'),
      back = el.querySelector('.card__back'),
      backBottom = el.querySelector('.card__back .card__bottom');

  this.update = function(val) {
    val = ('0' + val).slice(-2);
    if (val !== this.currentValue) {
      if (this.currentValue >= 0) {
        back.setAttribute('data-value', this.currentValue);
        bottom.setAttribute('data-value', this.currentValue);
      }
      this.currentValue = val;
      top.innerText = this.currentValue;
      backBottom.setAttribute('data-value', this.currentValue);

      this.el.classList.remove('flip');
      void this.el.offsetWidth;
      this.el.classList.add('flip');
    }
  }
  
  this.update(value);
}

function getTimeRemaining(endtime) {
  var t = Date.parse(endtime) - Date.parse(new Date());
  return {
    'Total': t,
    'DÍAS': Math.floor(t / (1000 * 60 * 60 * 24)),
    'HORAS': Math.floor((t / (1000 * 60 * 60)) % 24),
    'MINUTOS': Math.floor((t / 1000 / 60) % 60),
    'SEGUNDOS': Math.floor((t / 1000) % 60)
  };
}

function Clock(countdown, callback) {
  countdown = countdown ? new Date(Date.parse(countdown)) : false;
  callback = callback || function() {};
  
  var updateFn = countdown ? getTimeRemaining : getTime;

  this.el = document.createElement('div');
  this.el.className = 'flip-clock';

  var trackers = {},
      t = updateFn(countdown),
      key, timeinterval;

  for (key in t) {
    if (key === 'Total') { continue; }
    trackers[key] = new CountdownTracker(key, t[key]);
    this.el.appendChild(trackers[key].el);
  }

  var i = 0;
  function updateClock() {
    const iframe= document.getElementById("contador");
    console.log("l> iframe.contentWindow.document.body.scrollHeight");
    iframe.style.height = iframe.contentWindow.document.body.scrollHeight + "px";

    timeinterval = requestAnimationFrame(updateClock);
    
    if (i++ % 10) { return; }
    
    var t = updateFn(countdown);
    if (t.Total < 0) {
      cancelAnimationFrame(timeinterval);
      for (key in trackers) {
        trackers[key].update(0);
      }
      callback();
      return;
    }
    
    for (key in trackers) {
      trackers[key].update(t[key]);
    }
  }

  setTimeout(updateClock, 500);
}

// Configuración de la nueva fecha límite
var deadline = new Date("2024-12-09T12:00:00");
var c = new Clock(deadline, function() { alert('EMPIEZA A EXPLORAR'); });
document.body.appendChild(c.el);