classList.js

/*
 * classList.js
 *
 * Implements a cross-browser element.classList getter.
 *
 */

"use strict";

if (typeof Element !== "undefined") {

(function () {

var classListProp = "classList";

if (!Element.prototype.hasOwnProperty(classListProp)) {
	var trim = /^\s+|\s+$/g,
	setClasses = function (elem, classes) {
		elem.className = classes.join(" ");
	},
	checkAndGetIndex = function (classes, token) {
		if (token === "") {
			throw "SYNTAX_ERR";
		}
		if (/\s/.test(token)) {
			throw "INVALID_CHARACTER_ERR";
		}
		
		return classes.indexOf(token);
	},
	classListGetter = function () {
		var elem = this,
		classes  = elem.className.replace(trim, "").split(/\s+/);
		return {
			length: classes.length,
			item: function (i) {
				return classes[i] || null;
			},
			contains: function (token) {
				return checkAndGetIndex(classes, token) !== -1;
			},
			add: function (token) {
				if (checkAndGetIndex(classes, token) === -1) {
					classes.push(token);
					this.length = classes.length;
					setClasses(elem, classes);
				}
			},
			remove: function (token) {
				var index = checkAndGetIndex(classes, token);
				if (index !== -1) {
					classes.splice(index, 1);
					this.length = classes.length;
					setClasses(elem, classes);
				}
			},
			toggle: function (token) {
				if (checkAndGetIndex(classes, token) === -1) {
					this.add(token);
				} else {
					this.remove(token);
				}
			},
			toString: function () {
				return elem.className;
			}
		};
	};
	
	if (Object.defineProperty) {
		Object.defineProperty(Element.prototype, classListProp, { get: classListGetter });
	} else if (Object.prototype.__defineGetter__) {
		Element.prototype.__defineGetter__(classListProp, classListGetter);
	}
}

}());

}