A shim for jQuery that uses the native "classList" property of an element for class modifications, if available.

jquery.classlist.js

/*global jQuery */
;(function($) {

	/*global document */
	"use strict";

	if (typeof document !== 'undefined' && ('classList' in document.createElement('a'))) {

		var $ = jQuery;

		var _addClass = $.fn.addClass;
		var _removeClass = $.fn.removeClass;

		$.fn.hasClass = function(selector) {
			var elem, i, l;
			for (i = 0, l = this.length ; i < l; ++i) {
				elem = this[i];
				if (elem.nodeType === 1 && elem.classList.contains(selector)) {
					return true;
				}
			}
			return false;
		};

		$.fn.addClass = function(value) {
			var elem, i, l;	
			if (typeof value === 'string' && value && value.indexOf(' ') < 0) {
				for (i = 0, l = this.length ; i < l; ++i) {
					elem = this[i];
					if (elem.nodeType === 1) {
						elem.classList.add(value);
					}
				}
			} else {
				_addClass.apply(this, arguments);
			}
			return this;
		};

		$.fn.removeClass = function(value) {
			var elem, i, l;	
			if (typeof value === 'string' && value && value.indexOf(' ') < 0) {
				for (i = 0, l = this.length ; i < l; ++i) {
					elem = this[i];
					if (elem.nodeType === 1) {
						elem.classList.remove(value);
					}
				}
			} else {
				_removeClass.apply(this, arguments);
			}
			return this;
		};
	}

})(jQuery);