JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://underscorejs.org/underscore-min.js"></script>
<input id="filing_priority_enabled" name="filing[priority_enabled]" type="checkbox" checked>

<div class="js-dependent-fields" data-checkbox-id="filing_priority_enabled" data-checkbox-value="true">
<h1>This text is only shown if the checkbox above is checked.</h1>
</div>

JavaScript

// dependent fields js, see user code below

(function() {
  var bind, showOrHideDependentFieldsCheckbox, showOrHideDependentFieldsSelect, toggle;

  toggle = function($parent, showOrHide, method, duration) {
    if (showOrHide) {
      if (method === 'disable') {
        $parent.find('input,textarea,select,button,.btn').removeAttr('disabled');
        return $parent.find('.select2').select2('enable');
      } else {
        return $parent.show(duration);
      }
    } else {
      if (method === 'disable') {
        $parent.find('input,textarea,select,button,.btn').attr('disabled', 'disabled');
        return $parent.find('.select2').select2('disable');
      } else {
        return $parent.hide(duration);
      }
    }
  };

  showOrHideDependentFieldsSelect = function(duration) {
    var $select, showOrHideFields;

    if (duration == null) {
      duration = 'fast';
    }
    $select = $(this);
    showOrHideFields = function() {
      var $this, showOrHide;

      $this = $(this);
      showOrHide = _.contains($this.attr('data-option-value').split('|'), $select.val());
      return toggle($this, showOrHide, $this.data('method'), duration);
    };
    return $(".js-dependent-fields[data-select-id=" + ($select.attr('id')) + "]").each(showOrHideFields);
  };

  showOrHideDependentFieldsCheckbox = function(duration) {
    var $checkbox, showOrHideFields;

    if (duration == null) {
      duration = 'fast';
    }
    $checkbox = $(this);
    showOrHideFields = function() {
      var $this, showOrHide;

      $this = $(this);
      showOrHide = $this.data('checkbox-value') === $checkbox.is(':checked');
      return toggle($this, showOrHide, $this.data('method'), duration);
    };
    return $(".js-dependent-fields[data-checkbox-id=" + ($checkbox.attr('id')) + "]").each(showOrHideFields);
  };

  bind = function() {
    var $inputs, $selects;

    $selects = $('select');
    $selects.not('[data-important]').each(_.partial(showOrHideDependentFieldsSelect, 0));
   ...