title: jquery error: val() is not a function
body: <p>Why I'm getting this error? <code>val is not a function</code> when I validate the number.</p>
  
  <pre><code>$(this).find('#register-validation .next').click(function() {
       var _parent = $(this).parents('#register-validation');
       $('.loading-big').html(loadMsg).fadeIn(300);
       _parent.find('input.required').each(function(index) {
           if($(this).val() == "" || $(this).val() == errReq) { // here is fine
               $(this).val(errReq);
               $(this).addClass("error");
           }
           else if(isNaN($(this).hasClass('number').val())) { // but when validation goes here, I got this error.
               $(this).val(errNum);
               $(this).addClass("error");
           }
           else {
               $(this).removeClass("error");
           }
       });
  });
  </code></pre>
  
  <p>Please help. Thanks a lot.</p>