JavaScript function to manage CSS classes (detects native browser support)

element-classes.js

var Classes = (function () {
    "use strict";

    var E, trim, containsClass, addClass, removeClass, toggleClass;

    E = document.createElement("div");

    if (E.classList && !E.hasOwnProperty("classList")) {
        containsClass = function (el, cls) {
            return el.classList.contains(cls);
        };
        addClass = function (el, cls) {
            return el.classList.add(cls);
        };
        removeClass = function (el, cls) {
            return el.classList.remove(cls);
        };
        toggleClass = function (el, cls) {
            return el.classList.toggle(cls);
        };
    } else {
        trim = (function () {
            var S, re, func;
            S = "";
            re = /^\s+|\s+$/g;
            if (S.trim && !S.hasOwnProperty("trim")) {
                func = function (str) {
                    str = "" + (str || "");
                    return S.trim.call(str);
                };
            } else {
                func = function (str) {
                    str = "" + (str || "");
                    return str.replace(re, "");
                };
            }
            return func;
        }());
        containsClass = function (el, cls) {
            return !!~(" " + el.className + " ").indexOf(" " + cls + " ");
        };
        addClass = function (el, cls) {
            if (!containsClass(el, cls)) {
                el.className += " " + cls;
                return true;
            }
            return false;
        };
        removeClass = function (el, cls) {
            el.className = trim((" " + el.className + " ").replace(" " + cls + " "));
        };
        toggleClass = function (el, cls) {
            if (!addClass(el, cls)) {
                removeClass(el, cls);
            }
        };
    }

    return {
        contains: containsClass,
        add: addClass,
        remove: removeClass,
        toggle: toggleClass
    };
}());