Animate elements in and out on scroll

animate.js

// onScroll animation
$(function() {

  var $window           = $(window),
      isTouch           = Modernizr.touch;

  if (isTouch) { $('.add-animation').addClass('animated'); }

  $window.on('scroll', revealAnimation);

  function revealAnimation() {

    // Showed...
    $(".add-animation:not(.animated)").each(function () {
      var $this     = $(this),
          offsetTop = $this.offset().top,
          scrolled = $window.scrollTop(),
          win_height_padded = $window.height();
      if (scrolled + win_height_padded > offsetTop) {
          $this.addClass('animated');
      }
    });
    // Hidden...
   $(".add-animation.animated").each(function (index) {
      var $this     = $(this),
          offsetTop = $this.offset().top;
          scrolled = $window.scrollTop(),
          win_height_padded = $window.height() * 0.8;
      if (scrolled + win_height_padded < offsetTop) {
        $(this).removeClass('animated')
      }
    });
  }

  revealAnimation();
});