There are 3 major types of storage is browsers up to date:
- IndexedDB. The future.
- localStorage. Limited in size and can be observed through the
storageevent. - WebSQL. Dropped by the W3C but it's still very present in the wild, with notable platforms like iOS and PhoneGap.
In the mobile world local cache and storage is very important for various reasons:
- faster loading times
- unreliable connections
- offline use
My particular use case is an app to be used "in the field" where you probably don't have a connection and you need to do data entry. My solution is to save to a local storage and sync to the server when a connection is available. The 5 MB of localStorage may not be enough in my case, but I won't be able to tell until the app is used by real users.
- Is there enough interest in this considering the availability of
localStorage? - Is it too early to use these technologies?
The goal is to use conditional loading to load one of 3 or 4 sub-modules: indexeddb, websql, localstorage and a fallback to memory.
- IndexedDB uses a key-based storage organized in "object stores".
- WebSQL uses SQL tables. WebSQL can be used as a fallback for object stores by matching a table to a store and using tables with two columns: a
keyand avaluecolumn which saves the object serialized as JSON. - IndexedDB uses structured cloning which is similar to
JSON.parse(JSON.stringify(obj)).
- Is falling back to localStorage a good idea considering the limited size and observability?
- Is the whole concept OK or is it too hackish?
- Should this include over-the-wire databases via some protocol?
The API aims to find the lowest common denominator between all implementations. A database requires:
- A
name. Required by both IndexedDB and WebSQL - A
version. Required by both IndexedDB and WebSQL - A structure, which means the name of each object store, tied to the version. Required by both IndexedDB and WebSQL
- A
sizein bytes. Required by WebSQL
A Storage constructor receives all these parameters and creates an instance with properties with the names of each object store:
var storage = new Y.Storage({
name: 'my database',
version: 1,
size: 5242880,
stores: ['fooStore', 'barStore']
});
Assert.isObject(storage.fooStore); // true
Assert.isObject(storage.barStore); // trueA Storage instance also has a close method that closes the database connection/session.
A Store object is created for each requested store in a property of the same name. A store can perform the following actions:
get. Retrieve an object by keyput. Insert or update an object by keyremove. Remove an object by keyclear. Remove all objects from the storecount. Count the objects in the store
All methods return a promise.
Example:
storage.fooStore.put('some key', { foo: 'bar' }).then(...);- Should
Storageinherit fromBasein order to use attributes for configuration and maybe firecloseorerrorevents? Aversionchangeevent is very important.
Updated the gist: just promises, no callbacks; all actions return promises. Also added the question to discuss if this should include over-the-wire databases.