title: Confirm a select2 selection
body: <p>I'm using select2 v4, and I'm trying to display a <code>confirm()</code> when the user selects an option from the dropdown. </p>
  
  <p>So I have the event <code>.on("select2:select", function(e) {})</code> and I want to prevent select2 if the users chooses cancel from the confirm dialog.</p>
  
  <p>I have the following:</p>
  
  <pre><code>    $("#select2users").select2().on("select2:select", function(e) { 
          var data = e.params.data;
  
          if(!confirm("Are you sure you want to ban this user?")) {
              e.preventDefault();
          }
      })
  </code></pre>
  
  <p><code>e.preventDefault();</code> doesn't seem to have any effect here.
  I've been searching and cannot achieve any decent answer. 
  How should I do it?</p>