check.js

    $('div.table').on('change', 'input', function () {
      var $targ = $(this),
          isChecked = $(this).is(':checked'),
          $checks = $('.table .checkbox input'),
          $checked = $checks.filter(':checked'),
          $sumlabel = $('.overview-summary label');

      // the checkbox update will be handled by its own handler
      // update this row
       $targ.closest('.tr').toggleClass('selected', isChecked);

      // update counter at the bottom
      $checked.length === 0 ? $sumlabel.removeClass() :
      $checked.length === $checks.length ? $sumlabel.addClass('checked').prev().prop('checked', true) :
      $sumlabel.removeClass('checked').addClass('some-checked').prev().prop('checked', false);

      $('.currently-checked').text($checked.length);

    })

    $('.overview-summary input').on('change', function () {
      var isChecked = $(this).is(':checked'),
          $checks = $('.table .checkbox input');
      
      $checks.each( function (i, ele) {
        $checks.eq(i).prop('checked', isChecked)
          .next('label').toggleClass('checked', isChecked);
          .closest('.tr').toggleClass('selected', isChecked);
      })

      $(this).next().removeClass('some-checked').toggleClass('checked', isChecked);
      $('.currently-checked').text(isChecked ? $checks.length : 0);
    })