What is causing this extra "undefined"?

I've created a form and I'm using jQuery to check all fields with the "required" class. If the value for a field is empty, I'll eventually have it append an error message to an error div.

Anyway, for some reason in my testing, I'm getting an extra "undefined" when I try to output the "name" attribute to the errors div.

Here's a live example: http://lab.willpracht.net/form.php Click the button at the top.

You'll notice the extra "undefined" before the firstName. Can anyone figure out what's causing that? I'm confused as hell.

Here's the js:

$('input[type="button"]').click(function(){

            var errors;

            // Disable the error message, if displayed.
            $('html').scrollTop(0);
            $('#error').fadeOut('slow');

            // Loop thru all required, check to see if empty.
            $('.required').each(function(){
                if($(this).val() === ''){ 
                    //errors += $(this).attr('id') + 开发者_JAVA技巧'<br />';
                    errors += $(this).attr('name') + '<br />';
                }
            });

            $('#error .texture').html(errors);
            $('#error').fadeIn('slow');

        });

Thanks, everyone :).

try to set var errors; to var errors="";

Define errors as a string:

var errors = "";

var errors; just declares a variable. Declaring a variable without setting a value keeps the value at undefined.