Multiple Drop Down’s on a Single Page

I have multiple drop down boxes, which point to links. When I click drop down 2 of 4, only the first drop down extends.

Do I need to number each drop down / button? If so, how do you do that?

<!DOCTYPE html> <html> <head> <meta name="viewport" content="width=device-width, initial-scale=1"> <style> .dropbtn {   background-color: #3498DB;   color: white;   padding: 16px;   font-size: 16px;   border: none;   cursor: pointer; }  .dropbtn:hover, .dropbtn:focus {   background-color: #2980B9; }  .dropdown {   position: relative;   display: inline-block; }  .dropdown-content {   display: none;   position: absolute;   background-color: #f1f1f1;   min-width: 160px;   overflow: auto;   box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);   z-index: 1; }  .dropdown-content a {   color: black;   padding: 12px 16px;   text-decoration: none;   display: block; }  .dropdown a:hover {background-color: #ddd;}  .show {display: block;} </style> </head> <body> <div class="dropdown">   <button onclick="myFunction()" class="dropbtn">Dropdown</button>   <div id="myDropdown" class="dropdown-content">     <a href="#home">Home</a>     <a href="#about">About</a>     <a href="#contact">Contact</a>   </div> </div>  <script> /* When the user clicks on the button,  toggle between hiding and showing the dropdown content */ function myFunction() {   document.getElementById("myDropdown").classList.toggle("show"); }  // Close the dropdown if the user clicks outside of it window.onclick = function(event) {   if (!'.dropbtn')) {     var dropdowns = document.getElementsByClassName("dropdown-content");     var i;     for (i = 0; i < dropdowns.length; i++) {       var openDropdown = dropdowns[i];       if (openDropdown.classList.contains('show')) {         openDropdown.classList.remove('show');       }     }   } } </script>  </body> </html>