This is a very minimalistic interface on top of the LocalStorage API to save key-value objects as one value to LocalStorage. Done a lot of times, but this one just does the most simplest of things. Quick, easy and safe :)

LocalStorageHandler.js

var LS = function() {

	/*
		LocalStorageHandler Class
		- emulates a more user friendly interface
		for the LocalStorage API
	*/
	var LocalStorageHandler = function() {

		this.key = "local";
		this.data = {};

		this.settings = {
      // call prototype.write each time .get or .flush is called
      // causing the data store to be saved immediately
			autoSave: false
		}

		// localStorage namespace shortcut
		this._ls = window.localStorage;

	}
	LocalStorageHandler.prototype = {

		// initialise LS
		init: function() {

			var self = this,
				revive = function() {
					// revives existing localStorage data
					var key = self.key,
						item = self._ls.getItem(key),
						check = new Promise(function(resolve, reject) {

							if(item) {
								resolve(item);
							} else {
								reject();
							}

						});

					check.then(function(data) {
						// key is existent
						// write LS data to self.data as JSON
						self.data = JSON.parse(data);
					}, function() {
						// key is not yet existent
						// write data key to LS
						self._ls.setItem(key, JSON.stringify(self.data));
					});

				};

			revive();

		},

		// set local storage keyname
		setKey: function(keyName) {
			this.key = keyName;
		},

		// set a key on this store
		set: function(key, property) {
			this.data[key] = property;

			if(this.settings.autoSave) {
				this.write();
			}

			return this.data[key];
		},

		// get a key from this store
		get: function(key) {
			return this.data[key];
		},

		// save this.data stringified to localstorage
		write: function() {
			this._ls.setItem(this.key, JSON.stringify(this.data));
		},

		// empty store
		flush: function() {
			this.data = {};

			if(this.settings.autoSave) {
				this.write();
			}

			return this.data;
		},

		// write a setting to this.settings
		setting: function(settingName, settingValue) {
			this.settings[settingName] = settingValue;
		}

	};

	return new LocalStorageHandler();

}();

// set the key to work with
LS.setKey("myLocalStorageKey");

// set a setting for lS
LS.setting('autoSave', true);

// this HAS to be called in order to work
LS.init();

// from this point, LS can be accessed and the methods get, set, write and flush
// will perform actions on localStorage.myLocalStorageKey

// LS.set('firstname', 'Koen')
// LS.get('firstname') => Koen
// LS.set('firstname', 'Job')
// LS.get('firstname') => Job
// LS.flush();
// LS.get('firstname') => undefined