form.html

<input type="text" id="cc_exp" />
<input type="hidden" id="exp_month" data-stripe="exp_month" />
<input type="hidden" id="exp_year" data-stripe="exp_year" />

form.js

$('#cc_exp').payment('formatCardExpiry').change(function() {
  var exp = $.payment.cardExpiryVal($(this).val());
  $('#exp_month').val(exp.month);
  $('#exp_year').val(exp.year);
  return true;
});