<!-- REVEAL SUBMIT BUTTON WHEN EMAIL IS VALIDATED --> 
<script>
  $(function(){

    // Only show submit button on proper email
    ;( function( $, window, document, undefined ) {
        'use strict';
        var form        = '.email-form',
            className   = 'email-active',
            submit      = 'input[type="submit"]',
            email       = 'input[type="email"]';
        $( form ).each( function(){
            var $form   = $( this ),
                $email  = $form.find( email ),
                $submit  = $form.find( submit ),
                val     = '';
            $email.on( 'keyup.addClassWhenEmail', function(){
                val = $email.val();
                $submit.toggleClass( className, val != '' && /^([\w-\.]+@([\w-]+\.)+[\w-]{2,12})?$/.test( val ) );    
            });
        });
    })( jQuery, window, document );
  })
</script>