AJAX - The Complete Reference

534 Part III: Advanced Topics

Approach Description Comments

Cookies Stores data in persistent

cookies (disk cookies), splitting

larger items across a number

of cookies to be concatenated

together upon retrieval.

Possible in any browser.

Subject to cookie cleansing

from privacy concerned users.

Size and browser limitations.

Network impact as the cookie storage

would be transmitted with every request.

Security impact as storage is sent in

requests.

Internet Explorer

Behaviors

Stores data relative using a

DHTML behavior bound to a page

element such as a <div> tag.

Internet Explorer–specific system.

A single page is limited to 64K of

persisted data with a whole domain limited

to 640K.

Without a special cleaning program it

may be difficult for users to dump this

information.

Flash storage Uses Flash shared object to

store data in browsers that

support Flash.

Most bridge between SWF file embedded

in page and JavaScript.

Shareable between browsers, unlike any

other mechanism.

By default you should be able to store

100KB of data in this system. It is

adjustable with user prompts.

Users unlikely to dump persisted data

as they are unaware of the storage

mechanism.

Native Browser

Storage (DOM

Storage)WhatWG

A globalStorage system is

natively available from supporting

browsers in JavaScript.

Can be shared across a range of domains

and sites. Could be open for abuse.

Only implemented in Firefox browsers at

this point in time.

According to the current spec, a 5MB

limit is currently defined, though this may

change, particularly if abused.

TABLE 10-3 Summary of Push-style Communications Approaches