scroll.js

  // SCROLL EVENT CAPTURE //

  var wheel = document.getElementById('wheel');

  function report(ammout) {

      clearTimeout(time);

      if(ammout > 0){
       time = setTimeout(previousPage, 300);
      }else{
       time = setTimeout(nextPage, 300);
      }
  }

  function callback(event) {
      var normalized;
      if (event.wheelDelta) {
          normalized = (event.wheelDelta % 120 - 0) == -0 ? event.wheelDelta / 120 : event.wheelDelta / 12;
      } else {
          var rawAmmount = event.deltaY ? event.deltaY : event.detail;
          normalized = -(rawAmmount % 3 ? rawAmmount * 10 : rawAmmount / 3);
      }
      report(normalized);
  }

  var event = 'onwheel' in document ? 'wheel' : 'onmousewheel' in document ? 'mousewheel' : 'DOMMouseScroll';
  window.addEventListener(event, callback);