What is it?
Javascript is a popular scripting language most commonly used
for web development.
The original intention behind Javascript was to produce a
Java-like scripting language that would be easier to use. The
syntax is similar to Java, and to Java's precursor C++.
Javascript is a superset of the Ecmascript language, a standard
maintained by the
European Computer
Manufacturers Association (Ecma). After Javascript was released
by Sun and Netscape, Microsoft released its own version, JScript,
and it was JScript that was submitted to Ecma as the basis of the
standard. Adobe Flash's Actionscript is another
Ecmascript-compatible language.
Javascript demand is high thanks to the spread of
Ajax (Asynchronous Javascript and XML), and it has long been
the most widely used scripting language.
It is also first choice for malware writers, with obfuscated
Javascript the second most prevalent malware type in Sophos's
monthly list of top malware threats.
Where did it originate?
Javascript was developed by Brendan Eich at Netscape, first
under the name Mocha, and then more formally as Livescript - the
name it would probably have kept if it had not been for Netscape's
agreement with Sun. Javascript was first deployed in the Netscape
Navigator browser in 1995.
What's it for?
Javascript is most commonly used for client-side scripting
applications that are embedded in HTML pages to enable the pages to
be more responsive to the user than a server-based function would
be.
This is the basis of the Ajax approach: instead of reloading the
whole page every time the user makes a change or request, the
application exchanges the minimum possible data with the server,
and the application remains available to the user.
As a result, Ajax applications can have the kind of rich user
interfaces usually only available with desktop applications. For
the same reasons, Javascript is often chosen for large parts of
web-based applications, such as
Gmail. Javascript is also widely found in web server side
applications.
Javascript supports prototyping as well as procedural and
object-oriented programming. Developers need to consider that, on
the client side, Javascript applications are likely to encounter an
extremely wide range of environments, browsers and browser
versions. Javascript is interpreted differently by the various
browser suppliers.
What makes it special?
Because of the uncertainties of the client-side environment and
the just-get-by nature of much programming, Javascript has a poor
reputation. There is a move to change this through something called
Unobtrusive Javascript, which separates Javascript functionality
from a web page's content and defines best practice to avoid
problems such as browser inconsistencies.
As a result of this - and with Ajax in mind - Javascript is
being considered for more substantial applications than form
validation and altering images in response to mouse movements.
How difficult is it to master?
Javascript was designed to be learned quickly by people with C++
and Java backgrounds.
What systems does it run on?
Most browsers, and tools such as Adobe's Flash, Acrobat and
Dreamweaver.
More hot skills
➔ www.computerweekly.com/hotskills
Classroom-based Javascript training is available, and there are
plenty of good, free internet tutorials. Javascript creator Brendan
Eich has posted material in various places online and has
co-written a book on the subject, The Javascript Bible.
➔ http://javascript.internet.com
➔ http://java.sun.com/javascript
training
rates of pay
Javascript developers earn between £20,000 and £35,000,
depending on seniority and skills, and potentially much more with
Ajax experience. Computer Weekly/SSL salary survey
➔ www.computerweekly.com/ssl