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EXPIRATION.md

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Expiration

This lib, as native localStorage and indexedDb, is about persistent storage.

Misconceptions

Wanting temporary storage (like sessionStorage) is a very common misconception: an application doesn't need that.

This misconception comes from how we were (and still are) doing websites. As the user browses accross pages, it may be necessary to save some data in:

  • localStorage if we need to keep it even when he/she will leave the website and come back later,
  • sessionStorage if we don't need to keep it for later, but just while browsing the website.

But now with tools like Angular, from the technical side, we're building applications, not websites anymore. Even if we may distribute our application as what's look like as a website from the user side.

So it means the page never changes or reloads, so JavaScript is running as long as the user doesn't quit the app. So if we want to keep some data just while the user is here, we just need to store it in a classic variable, constant or property. You don't need local storage at all, neither temporary nor persistent.

If there are many of them, we may need to organize them in what we call a store, but it would still be just variables.

To summarize:

  • for persistent storage (if the user leaves and comes back later): localStorage (or this lib)
  • for temporary storage (just when the user is browsing):
    • sessionStorage in a website
    • just variables, constants and properties in an application

Tabs

The only case where sessionStorage can be legitimate in an application is if you need to share data between multiple tabs.

But it's an uncommon scenario, which can only happen if your app is distributed as a website (it has no sense on mobile or in a desktop app).

If you really are in this case, you'll have to stick to the native sessionStorage API. No lib can help you on this, as it's not possible to manage temporary data in indexedDb, and manually detecting when the user leaves is unreliable (as the browser won't always fire the unload event, for privacy reasons).

Theoretical persistency

Let's also make clear that this lib, as native localStorage and indexedDb, is about persistent storage, but persistent is to understand at a theoretical level.

In practice, data may be deleted if:

  • the storage becomes full, so the browser will do some cleaning
  • the user can manually force the cleaning of all local data (but note that the default cleaning options in browsers do not delete this kind of storage)