scripts.js

 var dropdown = document.getElementsByClassName("dropdown-btn");
 var i;

 for (i = 0; i < dropdown.length; i++) {
   dropdown[i].addEventListener("click", function() {
      this.classList.toggle("active");
      var dropdownContent = this.nextElementSibling;
      if (dropdownContent.style.display === "block") {
        dropdownContent.style.display = "none";
      } 
      else {
        dropdownContent.style.display = "block";
      }
    });
}
 
function openTab(evt, tabName) {
  // Declare all variables
  var t, tabcontent, tablinks;

  // Get all elements with class="tabcontent" and hide them
  tabcontent = document.getElementsByClassName("tabcontent");
  for (t = 0; t < tabcontent.length; t++) {
    tabcontent[t].style.display = "none";
  }

  // Get all elements with class="tablinks" and remove the class "active"
  tablinks = document.getElementsByClassName("tablinks");
  for (t = 0; t < tablinks.length; t++) {
    tablinks[t].className = tablinks[t].className.replace(" active", "");
  }

  // Show the current tab, and add an "active" class to the button that opened the tab
  document.getElementById(tabName).style.display = "block";
  evt.currentTarget.className += " active";
}