title: How to append only once? jQuery
body: <p>What I am trying to do is to append text to <code>.showError</code> only once every time you click on the button. Right now it appends each time you click on the button and get multiple times text appended to <code>.showError</code>. How do I prevent this from happening?</p>
  
  <pre><code>$("#send").on("click", function(ev) {
       $(".error-holder").empty();
       var err = 0;
       $("form .form-control").each(function(i, v) {
         if ($(this).val() == "") {
           err = 1;
         }
       });
  
       if (err == 1) {
         ev.preventDefault();
         $(".showError").append("Bij dit product moeten er serienummers ingevuld worden! &lt;br /&gt;&lt;br /&gt;");
         ($('#myModal').modal());
  
       }
  });
  </code></pre>