$(function () {

  var $navbar = $('[data-navbar]');
  var $logo = $('[data-float-logo]');
  var showFlag = getNeedShow();

  function getNeedShow() {
    return (window.scrollY >= $navbar.outerHeight(true));
  }

  function checkVisibility() {
    var needShow = getNeedShow();
    if (needShow != showFlag) {
      showFlag = needShow;
      $logo.toggleClass('show', needShow);
    }
  }

  var callback = _.throttle(checkVisibility, 100);

  $(window).on('scroll', callback);
  $(window).on('resize', callback);
  
});