index.js

$(document).ready(function () {
  $("a").on('click', function (event) {
    var hash = this.hash;
    $('body,html').animate({
      scrollTop: $(hash).offset().top
    }, 0, function () {
      window.location.hash = hash;
    });
  });
});

var width = $(window).width();

window.onscroll = function () {
  if ((width >= 900)) {
    if (document.body.scrollTop > 80 || document.documentElement.scrollTop > 80) {
      $("#middle").css("background-size", "150% auto");
    } else {
      $("#middle").css("background-size", "100% auto");
    }
  }
};

setTimeout(function () {
  $("#loading").addClass("animated fadeOut");
  setTimeout(function () {
    $("#loading").removeClass("animated fadeOut");
    $("#loading").css("display", "none");
  }, 800);
}, 1450);