$('form').each((i, form) => {

  const $form = $(form);

  const $count = $form.find('input#count');

  const $range = $form.find('input#range');

  const $total = $form.find('var#total');

  const $submit = $form.find('button#submit');

  const data = {};

  let total = 0;

  $form

    .on('input change', ({target, target: {id, value, checked}}) => {

      switch (id) {

        case 'price': {

          if (value == data.price) return false;

          data.price = value;

          break;

        }

        case 'count':

        case 'range': {

          if (value == data.count) return false;

          let v = value;

          if (id == 'count') {

            if (v < 0) {

              $count.val(0);

              v = 0;

            } else if (v > 100) {

              $count.val(100);

              v = 100;

            }

            $range.val(v);

          } else {

            $count.val(v);

          }

          data.count = v;

          break;

        }

        case 'shipping': {

          if (value == data.shipping) return false;

          data.shipping = checked;

          break;

        }

      }

      total = data.price * data.count;

      if (data.shipping) total += 2 * data.count;

      if (isNaN(total)) total = 0;

      $total.text(total);

      $submit.prop('disabled', !total);

      return false;

    })

    .on('submit', e => {

      if (total) alert(total);

      return false;

    });

});