Adds a Check All Option to a group of Checkboxes in Drupal jQuery Plugin

jquery.drupal_check_all.js

/**
 * Adds a Check All Option to a group of Checkboxes in Drupal jQuery Plugin
 *
 * To make this work you need pass to this function, a div that is a decendent
   of a form and an ancestor of multiple checkboxes. It is specifically tuned to
   drupal, but can be used for any html by setting the options. Here's and
   example, where .form-item-list is fapi element of type checkboxes.
 *
 * @code
 *  $('#my-form .form-item-list').drupalCheckAll();
 * @endcode
 *
 * @param options
 * - label: What should it say, default is 'Check All'; this will be sent
   through Drupal.t if that method exists
 * - location: 'top' or 'bottom'
 * - prefix: html to prepend to the new checkbox element
 * - suffix: html to append to the new checkbox element
 * - id: a specific id to add to the new checkbox element
 * - callback: a function to fire on click
 *
 * @return $(this)
 *
 * @author Aaron Klump, In the Loft Studios, LLC
 * @see http://www.intheloftstudios.com
 * @see https://gist.github.com/4261607
 */
(function($) {
  $.fn.drupalCheckAll = function(options) {

    // Create some defaults, extending them with any options that were provided
    var settings = $.extend( {
      'label'     : 'Check All',
      'location'  : 'prepend',
      'prefix'    : '<div class="form-item">',
      'id'        : $(this).parents('form').attr('id') + '-trigger',
      'classes'   : 'form-checkbox drupal-check-all-trigger',
      'suffix'    : '</div>',
      'children'  : '.form-checkbox',
      'callback'  : null
    }, options);

    var $wrapper = $(this);
    // Do not apply if total children is less than 2
    if ($wrapper.find(settings.children).length < 2) {
      console.log($wrapper.find(settings.children).length);
      return $(this);
    }
    
    // Check if we can translate (the test is for portability outside Drupal)
    if (Drupal.t !== undefined) {
      settings.label = Drupal.t(settings.label);
    }

    var $toggle = $(settings.prefix + '<input id="' + settings.id + '" type="checkbox" class="' + settings.classes + '"> <label for="' + settings.id + '" class="option">' + settings.label + '</label>' + settings.suffix);

    switch (settings.location) {
      case 'bottom':
        $wrapper.append($toggle);
        break;
      case 'top':
      default:
        $wrapper.prepend($toggle);
        break;
    }
    
    var $all = $wrapper.find(settings.children).not('.drupal-check-all-trigger');

    // Select checkbox if all children are selected
    $toggle.find(settings.children).attr('checked', $all.filter(':not(:checked)').length == 0 ? true : false);

    // Ensure that check all value matches value of children
    $all.click(function() {
      $toggle.find(settings.children).attr('checked', $all.filter(':not(:checked)').length == 0 ? true : false);
    });
    
    // Click handler
    $toggle.find(settings.children).click(function(){
      var state = $(this).is(':checked');
      var $children = $wrapper.find(settings.children);
      $children.attr('checked', state);
      // Fire callback if provided
      if (options.callback) {
        $form = $wrapper.parents('form');
        options.callback($form, $children);
      }
    });

  	return $(this);
  };
})(jQuery);