Animated Accordion [closed]

Since you already loading JQuery, add the following $('document'):

(function($) {

$(window).load(function() { //lets wait for all to be loaded

  alert("Accordion script loaded");
  var acc = document.getElementsByClassName("accordion");
  var i;

  for (i = 0; i < acc.length; i++) {
    acc[i].onclick = function() {
      this.classList.toggle("active");
      var panel = this.nextElementSibling;
      if (panel.style.maxHeight){
        panel.style.maxHeight = null;
      } else {
        panel.style.maxHeight = panel.scrollHeight + "px";
      } 
    }
  }

});

})(jQuery);

looks like document.getElementsByClassName("accordion"); its returning NULL and you are trying to set the style property of it, this due to the script running too early, so nothing is found.