Sunday, March 31, 2013

JavaScript: The less known parts. Storage.

'JavaScript: The less known parts' chapters:
1. Bitwise Operators
2. Storage
3. Dom Mutations

Client side storage is almost as old as Internet itself. Back in the days we used cookies for this, but since Firefox 2 & Safari 4 browsers support DOM Storage techniques. We are probably all familiar with IndexedDB or deprecated WebSQL. Both of them are widely supported in almost all of the newest browsers:


Thats not all - we also have well known localStorage & sessionStorage key/value client storage system. We can simply save the value in one window:
And load it in another:

The advantage of local/session storage over IndexedDB is that we can listen to an event that fires when something has changed - we can for instance propagate those changes to all the browser cards or iframes in our application. Choose the 'result' tab in the next fiddle, go back to the first one and save something using the form.
It's helpful also in IndexedDB based apps - for example PouchDB made by Dale Harvey use localStorage events with IndexedDB data to keep everything up to date everywhere. storage

We can also use property to store data on the client side. This ancient method allows us to read and write data across pages and domains, even from outside the current origin. According to Wikipedia [HTTP COOKIE] we can store up to 32MB there (according to some sources its even around 60MB). It's also accessible even before domready event. And even if it's not really cleaver idea in times of tabbed browsing (every new tab starts with empty, it's still used as a fallback in for older browsers. More on storage:
Ajaxian: What’s in a
Cookie-less Session Variables in JavaScript
Session variables without cookies
HTML5 sessionStorage for "every" browsers

See you next Monday in the 3rd part of Javascript: The less known parts. Follow me on Twitter and stay informed about next parts!


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