Backbone.js + Local Connection cache example

cache.js

/*global require, define, console, Modernizr */

define([
	"jquery",
	"backbone"
], function ($, Backbone) {

	var storage = {};

	if (Modernizr.localstorage) {
		storage = window.localStorage;
	}

	var cache = {
		get : function (key) {
			return storage[key];
		},

		set : function (key, value) {
			return storage[key] = value;
		},

		has : function (key) {
			return storage[key] !== undefined;
		},

		remove : function (key) {
			delete storage[key];
		}
	};

	var sync = Backbone.sync;

	Backbone.sync = function (method, model, options) {

		var allowCache = options.cache || false;
		var expires = options.cacheExpires || 60*60;

		var hasCache;
		var expireDate = 0;
		var url;
		var success;
		var data;

		// TODO: Add cache name id support

		if (method === "read" && allowCache) {

			success = options.success;
			url = model.url();
			hasCache = cache.has(url);

			if (hasCache) {
				expireDate = Number(cache.get("expires:"+url));
			}
			
			// Restore from cache
			if (hasCache && expireDate>new Date().getTime()) {
				data = cache.get(url);
				options.success(cache.get(url), "success");
				return $.ajax();

			// Save to cache
			} else {
				options.success = function (resp, status, xhr) {
					expireDate = new Date().getTime()+(expires*1000);
					cache.set("expires:"+url, expireDate);
					cache.set(url, resp);
					success(resp, status, xhr);
				};
			}
		}

		return sync.apply(Backbone, arguments);
	};

	return cache;
});