tldr: Someone wrote a bunch of paragraphs and LOC around JSON.parse(window.localStorage.getItem(key)).

If you're really interested in learning about creating a workable offline web app, Google has some great documentation. https://developers.google.com/web/fundamentals/instant-and-o...

Last, the Safari team needs to seriously get to work on Service Workers. We will see web apps grow by leaps and bounds once the service worker spec is opened up to iPhone users.