storage.js

var ls = {
    getItem: function (key) {
        var value = localStorage.getItem(key);

        try {
            value = JSON.parse(value);
        } catch (error) {
            value = value;
        }

        return value;
    },

    setItem: function (key, value) {
        if (typeof value !== 'string') {
            value = JSON.stringify(value);
        }

        localStorage.setItem(key, value);
    },

    removeItem: function (key) {
        localStorage.removeItem(key);
    },

    clear: function(pattern) {
        if (pattern) {
            for (var item in localStorage) {
                if (item.match(pattern)) {
                    localStorage.removeItem(item);
                }
            }
        } else {
            localStorage.clear();
        }
    },

    key: function (index) {
        return localStorage.key(index);
    },

    size: function() {
        return localStorage.length;
    }
}