Local Storage:

Historically, web applications have had none of these luxuries. Cookies were invented early in the web’s history, and indeed they can be used for persistent local storage of small amounts of data. But they have three potentially dealbreaking downsides:

• Cookies are included with every HTTP request, thereby slowing down your web application by needlessly transmitting the same data over and over
• Cookies are included with every HTTP request, thereby sending data unencrypted over the internet (unless your entire web application is served over SSL)
• Cookies are limited to about 4 KB of data — enough to slow down your application (see above), but not enough to be terribly useful

USING HTML5 STORAGE HTML5 Storage is based on named key/value pairs. You store data based on a named key, then you can retrieve that data with the same key. The named key is a string. The data can be any type supported by JavaScript, including strings, Booleans, integers, or floats. However, the data is actually stored as a string. If you are storing and retrieving anything other than strings, you will need to use functions like parseInt() or parseFloat() to coerce your retrieved data into the expected JavaScript datatype.

```interface Storage { getter any getItem(in DOMString key); setter creator void setItem(in DOMString key, in any data); };

Calling setItem() with a named key that already exists will silently overwrite the previous value. Calling getItem() with a non-existent key will return null rather than throw an exception.

Like other JavaScript objects, you can treat the localStorage object as an associative array. Instead of using the getItem() and setItem() methods, you can simply use square brackets. For example, this snippet of code:

var foo = localStorage.getItem("bar");

localStorage.setItem(“bar”, foo); …could be rewritten to use square bracket syntax instead:

var foo = localStorage[“bar”]; // … localStorage[“bar”] = foo;

There are also methods for removing the value for a given named key, and clearing the entire storage area (that is, deleting all the keys and values at once).

interface Storage { deleter void removeItem(in DOMString key); void clear(); }; Calling removeItem() with a non-existent key will do nothing. ````

At time of writing, IndexedDB has only been implemented in a beta version of Firefox 4. (By contrast, Mozilla has stated that they will never implement Web SQL Database.) Google has stated that they are considering IndexedDB support for Chromium and Google Chrome. And even Microsoft has said that IndexedDB “is a great solution for the web.”

So what can you, as a web developer, do with IndexedDB? At the moment, virtually nothing beyond some technology demos. A year from now? Maybe something. Check the “Further Reading” section for links to some good tutorials to get you started