simple_jq_signup.js

$.ajaxSetup({crossDomain : true});
var url = 'https://your-url-is-here.com';

var handleSuccess = function(resp) {
  $('.loader').hide();
  $('.email_input').val('');
  $('.thanks').show();
};

var handleError = function(resp) {
  $('.loader').hide();
  $('.error').show();
};

var submitSubscription = function() {
  var emailRE = /.+\@.+\..+/;
  var email = $('.email_input').val();
  var isEmailValid = emailRE.test(email);
  if (!email || !isEmailValid) { return false; }
  $('.loader').show();
  var willSubmit = $.post(url, {email: email});
  willSubmit.done(handleSuccess);
  willSubmit.fail(handleError);
};

$('.sign_up_button').click(function(e) {
  submitSubscription(e);
});

$('.email_input').on('keyup', function(e) {
  $('.error').hide();
  if (e && e.keyCode === 13) {
    submitSubscription(e);
  }
});