Local&Sesion storage shiv

if (typeof window.localStorage == 'undefined' || typeof window.sessionStorage == 'undefined') (function () {

    var Storage = function (type) {
        function createCookie(name, value, days) {
            var date;
            var expires;

            if (days) {
                date = new Date();
                date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
                expires = "; expires=" + date.toGMTString();
            } else {
                expires = "";
            }
            document.cookie = name + "=" + value + expires + "; path=/";
        }

        function readCookie(name) {
            var nameEQ = name + "=";
            var ca = document.cookie.split(';');

            for (var i = 0; i < ca.length; i++) {
                var c = ca[i];
                while (c.charAt(0) == ' ') {
                    c = c.substring(1, c.length);
                }

                if (c.indexOf(nameEQ) == 0) {
                    return c.substring(nameEQ.length, c.length);
                }
            }
            return null;
        }
        function setData(data) {
            data = JSON.stringify(data);
            if (type == 'session') {
                window.name = data;
            } else {
                createCookie('localStorage', data, 365);
            }
        }
        function clearData() {
            if (type == 'session') {
                window.name = '';
            } else {
                createCookie('localStorage', '', 365);
            }
        }
        function getData() {
            var data = type == 'session' ? window.name : readCookie('localStorage');
            return data ? JSON.parse(data) : {};
        }


        // initialise if there's already data
        var data = getData();

        return {
            length: 0,
            clear: function () {
                data = {};
                this.length = 0;
                clearData();
            },
            getItem: function (key) {
                return data[key] === undefined ? null : data[key];
            },
            key: function (i) {
                var ctr = 0;
                for (var k in data) {
                    if (ctr == i) return k;
                    else ctr++;
                }
                return null;
            },
            removeItem: function (key) {
                delete data[key];
                this.length--;
                setData(data);
            },
            setItem: function (key, value) {
                data[key] = value + '';
                this.length++;
                setData(data);
            }
        };
    };

    if (typeof window.localStorage == 'undefined') window.localStorage = new Storage('local');
    if (typeof window.sessionStorage == 'undefined') window.sessionStorage = new Storage('session');

})();