title: Use javascript to add a CSS class to all elements with another class name
body: <p>I am trying to use javascript to add a Class  to all elements with a different Class. I know you might think this is redundant but for the situation i am in it is needed. i need a way to look though all elements with that class name and add the class but I don't understand how to get a count?  I am working with a cms to where I cannot change the styling in the class it self.</p>
  
  <pre><code>$(document).ready(function () {
              var ClassBtn = document.getElementsByClassName("buttonSubmit");
  
              ClassBtn.className = ClassBtn.className + " btn";
  
  
          });
  </code></pre>