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III. Introduction to JavaScript
JavaScript is an easy-to-learn programming language that can be built into Web pages, so
that it executes from within the browser rather than on the web server. Intranets especially
can leverage the power of JavaScript to create "smart" Web pages that can process data
and interact with the user. In this introduction, we concisely look at the main programming
points of the JavaScript language. This introduction is intended to be very short and brief.
For a much more in-depth discussion, please visit the LoudOffice.com class website and
download the Guide to JavaScript there.

Versions of JavaScript
There are several versions of JavaScript supported by certain browsers and browser
versions. Unfortunately, this can often lead to confusion and incompatibilities. Since
Netscape originally introduced JavaScript, JavaScript 1.0 was the language specification
supported in Netscape Navigator 2.0. Subsequently, Navigator 3.0 supported new
enhancements which comprised JavaScript 1.1. At present, Navigator 4.0 versions below
4.05 inclusive support JavaScript 1.2 while Navigator 4.06+ and the Netscape
Communicator 4.5+ series support JavaScript 1.3.

Shortly after Netscape's introduction of JavaScript in Navigator 2.0, Microsoft attempted to
support JavaScript 1.0 in their Internet Explorer 3.0 browser. Known as "Jscript," Microsoft's
initial JavaScript support was unreliable and buggy. A push to standardize the language
resulted in an "official" version of JavaScript sanctioned by the ECMA, an international
standards body. Both Internet Explorer 4.0 JScript and Netscape's JavaScript 1.3 are ECMA-
compliant and therefore the most compatible with one another. Internet Explorer 5
introduces additional extensions to the present ECMA standard which are not yet supported
in kind by Netscape.

As you can see, the ongoing browser war takes a great toll on web development at the
JavaScript level. Because of the variation in support for JavaScript/JScript across browser
revisions, and quite a few exceptions therein, it is impossible to say that any two browser
versions are completely compatible with one another. For many web developers, authoring
JavaScript code which gracefully accounts these in JavaScript support is an enormous
challenge. Intranet developers may have the unique advantage of being able to focus on a
single version of JavaScript in the case of intranets where only a single version of a single
browser is deployed. From the developer's perspective, this type of intranet policy greatly
eases the web development process, increasing both functionality and speed of
development.

Embedding JavaScript
JavaScript code is typically embedded into an HTML document using the SCRIPT tag. You
are free to embed as many scripts into a single document as you like, using multiple SCRIPT
tags. A script embedded in HTML with the SCRIPT tag uses the format:

< s c r i p t l a n g u a g e = " J a v a S c r i p t 1 . 2 " >
< ! - - / / H i d e F r o m O l d B r o w s e r s
. . .
/ / U n h i d e - - >
< / s c r i p t >

LoudOffice.com Guide to HTML – Part II Page 16