Web Storage API
From SpinetiX Support Wiki
The Web Storage API offers permanent & semi-permanent storage of structured data on the client side (HMP, Elementi), through its two global objects:
localStorage (permanent storage) and
sessionStorage (semi-permanent storage)
- It was introduced in 3.0.0 firmware release, to complement the Shared Variables API usage, especially in what concerns the permanent storage of data (i.e. resilience to player restarts). See also Project:LocalStorage tester.
- In 3.1.0 release, the Shared Variables framework was changed in order to have Shared Variables automatically saved into the localStorage object, thus having their values kept upon HMP reboots. Updating a Shared Variable triggers a modification within the localStorage object as well.
The maximum size for each of the two web storage objects is 4 MB. To remove the data stored into the web storage, use the
.clear() method on both
sessionStorage objects. Additionally, on the HMP side, this can also be done from HMP Control Center > Content Settings > Web storage tab.
localStorage object enables permanent storage of data, being resilient to player reboots.
localStorage object provides access to a list of key/value pairs (sometimes called items), that can be set and / or read with the following methods:
// setter localStorage.setItem(key, value); // getter localStorage.getItem(key); // remove item localStorage.removeItem(key); // remove all items from the local storage localStorage.clear();
sessionStorage object is identical to the
localStorage object as structure and as methods that can be used on it. The sole difference between them is that the former is reinitialized whenever the project starts (i.e. following a restart or a publish), while the latter is not.
// setter sessionStorage.setItem(key, value); // getter sessionStorage.getItem(key); // remove item sessionStorage.removeItem(key); // remove all items from the session storage sessionStorage.clear();
- When invoking the methods above, except for the getter, a storage event is fired.
- Comparing to Shared Variables, using
localStoragehas the advantage that the value of a item (i.e. object property) can be read at any time independently on the time it has been set.