What is it?
In April 2006, a reviewer provided a round-up of 50 different
Ajax frameworks and toolsets - and the number has certainly
increased since then. They include commercial start-ups, and plenty
of open-source efforts, many with small but devoted followings. For
Microsoft users, the choice is likely to be
ASP.net Ajax. Other developers may be looking for the freedom
of open source combined with the sponsorship of major technology
providers. For those who want access to a comprehensive and proven
Javascript library,
Dojo combines
a large open source community with the backing of IBM and Sun,
among others.
Dojo is a modular Javascript toolkit, which brings together a
number of contributed code bases to provide a unified, full stack
with a very small core and a large number of optional modules. IBM
has now adopted Dojo as its internal standard for Ajax, and
includes it with the
WebSphere
Application Server Feature Pack for
Web 2.0.
Where did it originate?
Dojo was begun in 2004 by Alex Russell of data integration
specialist Informatica. The Dojo community took off rapidly. In
2006, IBM made a large code contribution, including
internationalisation, accessibility for the disabled, extensions to
the data model, and some elements of its then-internal Ajax
toolkit. Sun also weighed in, contributing
Ajax widgets
and help with documentation, and the services of its own Ajax
Architect.
Other Dojo Foundation members and Dojo users include AOL and BEA
Systems.
What's it for?
Like other such toolkits, Dojo is intended to enable developers
to build dynamic pages and applications quickly and easily by
assembling functionality from libraries, which can then be tweaked
or extended with custom-written code.
The Dojo Core includes a package that simplifies the
XMLHttpRequest mechanism, which transfers data to and from the
server asynchronously, and which is key to the greater
responsiveness of Ajax applications. Dojo favours
Javascript Object Notation (JSON), a lightweight data
interchange standard, over XML, claiming it is often much
faster.
The Dojo widget library, Dijit, also provides a template-driven
architecture for building widgets. Dojo Storage enables persistent
storage of data on the client side.
Developers can use the (open-source)
Aptana IDE for Ajax, or the (paid-for)
Komodo IDE. IBM's involvement ensures Dojo is supported by the
Eclipse Ajax Toolkit Framework.
What makes it special?
Although there is a great deal of best-practice advice and
support for Dojo developers, innovation is encouraged. The Dojo
Style Guide, put together collectively by Dojo's core developers,
carries the rider "any violation to this guide is allowed if it
enhances readability".
How difficult is it to master?
The Dojo site includes a quick-start tutorial for newcomers
called "Dojo for the Attention-Impaired". Dojo has been designed to
be quick and easy to use. The sheer scale of it means that learning
to use it to its full potential will take time - but it can be
learned on the job.
What systems does it run on?
Dojo supports Internet Explorer, Safari, Firefox and Opera
Google Gears, which enables applications to work offline as well as
on and the Open
Ajax Alliance Hub, to ensure interoperability with Ajax
applications built with other toolkits.
Rates of pay
Ajax developers earn from £25,000 to £45,000.
Training
A quick start
guide is available online. There is plenty of Dojo material on
IBM's developerWorks.
Sun's resources for
Ajax and Dojo are
spread across
several portals.