StickyFooter.js

var StickyFooter = (function ($) {

  var $body      = $('html, body');
  var $footer    = $body.find('.main-footer');
  var $CTAfooter = $body.find('.cta-footer');

  function init() {
    if ($footer.length && $CTAfooter.length) {
      checkFooter();
      triggerEventScrolling(checkFooter);
    }
  }

  function checkFooter(){
    // by anteNando
    // using https://github.com/customd/jquery-visible
    // important thing here is to keep observing a static element (.main-footer) and set the fixed one (.cta-footer)
    // when the static is visible

    if (!isVisible($footer, true)) $CTAfooter.addClass('is-fixed');
    if (isVisible($footer, true)) {
      $CTAfooter.removeClass('is-fixed');
      return;
    }
    $CTAfooter.addClass('is-fixed');
  }

  function triggerEventScrolling(callback) {
    $(window).on('scroll', callback);
  }

  function isVisible(el, onViewport) {
    return el.visible(onViewport);
  }

  function isFixed() {
    return $CTAfooter.hasClass('is-fixed');
  }

  init();

  return {
    isFixed: isFixed
  }

})($);