Fallback to localStorage in Samsung Smart TV

localstorage.js

/**
 * Fallback to localStorage
 **/
;(function() {
    if (typeof localStorage == "undefined" && typeof FileSystem == "function") {
        var fileSyObj = new FileSystem();
        var fileName  = curWidget.id + "_localStorage.db";
        var lStorage  = {};
        var changed   = false;

        // load or init localStorage file
        var fileObj = fileSyObj.openCommonFile(fileName, "r+");
        if (fileObj != null) {
            try {
                lStorage = JSON.parse(fileObj.readAll());
            } catch(e) { }
        } else {
            fileObj = fileSyObj.openCommonFile(fileName, "w")
            fileObj.writeAll("{}");
        }
        fileSyObj.closeCommonFile(fileObj);

        // Save storage
        lStorage.saveFile = function(delay) {
            if (changed && typeof JSON == 'object') {
                var $self = this;
                var save  = function() {
                    fileObj = fileSyObj.openCommonFile(fileName, "w")
                    fileObj.writeAll(JSON.stringify($self));
                    fileSyObj.closeCommonFile(fileObj);
                    changed = false;
                }
                if (typeof delay != 'undefined' && delay)
                    setTimeout(save, 100);
                else
                    save();
            }
        }

        lStorage.setItem = function(key, value) {
            changed = true;
            this[key] = value;
            this.saveFile(true);
            return this[key];
        }

        lStorage.getItem = function(key) {
            return this[key];
        }

        window.localStorage = lStorage;
    }
})();

There's a slight difference between native localStorage and this implementation.
In native localStorage all values are stored as strings, while in this implementation the values keep their original type.

// native:
localStorage.setItem('test', 1);
localStorage.getItem('test'); // string '1'

// this implementation:
localStorage.setItem('test', 1);
localStorage.getItem('test'); // number 1

This might seem insignificant, but I had a very tricky bug related to that.
In order to fix that you need to change the line

this[key] = value;

to

this[key] = value.toString();