I am looking to add a custom message before listing my errors for a login page:

"Oops, you forgot to enter the following:" + "Username", "Password" (if both not entered)

or

"Oops, you forgot to enter the following:" + "Username" (if just username not entered)

$(document).ready(function(){
$("#loginForm").validate({

    errorLabelContainer: $('#RegisterErrors'),
    messages: {
      username: "Username",
      password: "Password"
              }
     });
      });     

With this in my HTML

<div id="RegisterErrors">