Simple checkbox toggling with jQuery

checkbox-toggle.js

/* global jQuery */

/**
 * Simple Checkbox Toggling
 *
 * Hands-free checked/unchecked toggling for all checkboxes.
 *
 * Requirements:
 * - jQuery
 * - `name="foo[]"` -- Name attribute must assign checked values to an array.
 * 
 * Options (passed to `event.data`):
 * - `all` -- The input value for the master toggler.
 * 
 * Example:
 * ```html
 * <input type="checkbox" id="category-all" name="category[]" value="all">
 * <label for="category-all">Select All/None</label>
 * ```
 * 
 * Features:
 * - `data-checkbox-scoped` -- Add this data attribute to the parent
 *   of a collection of checkboxes to scope a set as a subset.
 * 
 * Todo:
 * - Exclude "all" from form submission. Probably just replace its
 *   value/name attributes with data attributes.
 */

(function ($) {
	'use strict';

	function CheckboxToggle ( event ) {
		var $trigger, $checked, $checkboxes, $master, $scope;

		all = ( event.data && event.data.all ? event.data.all : 'all' );

		$trigger = $( event.currentTarget );

		$scope = $trigger.parents('[data-checkbox-scoped]');

		$checkboxes = $( ':checkbox[name="' + $trigger.attr('name') + '"]', ( $scope.length ? $scope : null ) ).not(':disabled');

		if ( all === $trigger.val() ) {
			$master = $trigger;

			$checkboxes = $checkboxes.not( $master );

			$checkboxes.prop( 'checked', $master.prop('checked') );
		}
		else {
			$master = $checkboxes.filter('[value="' + all + '"]');
			$checkboxes = $checkboxes.not( $master );

			$checked = $checkboxes.filter(':checked');

			if ( $master.length ) {

				$checkboxes = $checkboxes.not( $master );

				$master
					.prop( 'checked', $checked.length > 0 )
					.prop( 'indeterminate', ( $checked.length > 0 && $checked.length < $checkboxes.length ) );
			}
		}
	};

	$(document).on( 'change.toggle-checkboxes', ':checkbox[name$="[]"]', CheckboxToggle );

}(jQuery));