Source: dom/classes.js

/**
 * dom/classes.js is part of Aloha Editor project http://www.alohaeditor.org
 *
 * Aloha Editor ● JavaScript Content Editing Library
 * Copyright (c) 2010-2015 Gentics Software GmbH, Vienna, Austria.
 * Contributors http://www.alohaeditor.org/docs/contributing.html
 */
define([
	'dom/nodes',
	'arrays',
	'strings'
], function (
	Nodes,
	Arrays,
	Strings
) {
	'use strict';

	/**
	 * Uses a string modifier function such as Strings.addToList to
	 * modify the classList of an element
	 *
	 * @private
	 * @param {!Element}                   elem
	 * @param {function(...string):string} modify
	 * @param {Array.<string>} classes
	 */
	function modifyClassList(elem, modify, classes) {
		elem.className = Strings.uniqueList(modify.apply(
			null,
			[elem.className].concat(classes)
		));
	}

	/**
	 * Adds one or more classes to current classes of the given Element.
	 *
	 * @param {!Element}  elem
	 * @param {...string} className
	 * @alias addClass
	 * @memberOf dom
	 */
	function add(elem) {
		modifyClassList(elem, Strings.addToList, Arrays.coerce(arguments).slice(1));
	}

	/**
	 * Removes one or more class names from the given element's
	 * classList.
	 *
	 * @param  {!Element}  elem
	 * @param  {...string} className
	 * @alias removeClass
	 * @memberOf dom
	 */
	function remove(elem) {
		modifyClassList(elem, Strings.removeFromList, Arrays.coerce(arguments).slice(1));
	}

	/**
	 * Checks whether the given node has the specified class.
	 *
	 * @param  {Node}    node
	 * @param  {string}  value
	 * @return {boolean}
	 * @alias hasClass
	 * @memberOf dom
	 */
	function has(node, value) {
		return Nodes.isElementNode(node)
		    && node.className.trim().split(Strings.WHITE_SPACES).indexOf(value) >= 0;
	}

	function toggle(node, name, flag) {
		if (true === flag) {
			add(node, name);
		} else if (false === flag) {
			remove(node, name);
		} else {
			toggle(node, name, has(node, name));
		}
	}

	return {
		has    : has,
		add    : add,
		remove : remove,
		toggle : toggle
	};
});