title: javascript - adding a div inside an element received by getElementsByClassName
body: <p>Im really beginner to this so sorry if this question is very basic.
  I have a button with background-image and I want to insert a small little icon inside the button to appear on its backgound-image.</p>
  
  <p>Now, I'm getting the button element this way:</p>
  
  <pre><code>elements = document.getElementsByClassName("test");
  var div = document.createElement("innerdiv");
  div="";
  var element = elements[0];
  </code></pre>
  
  <p>I think all I need to do is insert a div inside the button div
  but how can I do this from here?</p>