Question

Notice it when you type a valid e-mail… then delete this email and it doesn’t hide submit button. There a jsFiddle:

http://jsfiddle.net/BGNsS/

Can anyone help me?

thx!

Answer 1

Check for a valid regex and the length. Your regex has success for a empty field.

You check the length of the collection of jQuery elements here

if(!$("#sForm input#write").length > 0) $("input#sub").hide();

But you must check the length of the value

detectEmail.length == 0

Updated jsFiddle

$('input#sub').hide();

$('input').keyup(function() {
    $('span.attention').hide();

    var detectEmail = $(this).val();
    var emailRegex = /^([\w-\.]+@([\w-]+\.)+[\w-]{2,4})?$/;

    if(detectEmail.length == 0 || !emailRegex.test(detectEmail)) 
    {
        $('#sub').hide();
        $(this).after('<span class="attention">Writing valid e-mail...</span>');
    }
    else 
    {
        $('#sub').show();
    }
});