Help! for Javascript

This document contains some hints on using JavaScript in your web pages. JavaScript is a programming language designed to add functionality to HTML. You do not have to know anything about programming to understand this document. However, some knowledge of HTML is helpful, especially if you are planning on reading further documentation.

What is it and where did it come from?
Can everyone use it?
Learning JavaScript

What is it and where did it come from?

JavaScript commonly refers to client-side JavaScript, a programming language developed by Netscape. Microsoft also has its own version, called JScript. Other things that have similar names: Java, a cross-platform programming language developed by Sun Microsystems, and server-side JavaScript, similar to CGI script and not supported by our server.

JavaScript is written directly into your HTML document, and can control which images are displayed on your web page, or display a message customized to each visitor to your web page, or do a number of other things that can make your pages more interactive.

Can everyone use it?

There are versions of JavaScript, just like there are versions of browsers. Older browsers support older versions of JavaScript, or don't support it at all. In addition, Microsoft's Internet Explorer can take a piece of JavaScript code and interpret it differently than Netscape Navigator does. In general, you need Netscape Navigator 2 or later, Internet Expolorer 3 or later, or the AOL browser version 4 or later to be able to use JavaScript. If you're interested in a lot of detail about Javascript/JScript implementation in different browsers, go to: http://www.digitalroom.net/javascript/index.html and http://www.mozilla.org/docs/web-developer/

Some browsers do not support JavaScript at all, such as text browsers. In order to hide your script from these browsers, enclose your script within HTML comment tags:

<!-- Hide your script from old browsers
alert("Good thing you don't have one of those old browsers")
// End hiding script from old browsers -->

You may also want to provide content for people using browsers that do not support JavaScript by using the <NOSCRIPT> tag:

<NOSCRIPT>
Text browsers rock! They just don't make browsers like they used to...
</NOSCRIPT>

You can see what your page will look like through a browser that doesn't support JavaScript by going to:
http://www.delorie.com/web/wpbcv.html
You must provide a URL for the page, which means that it must be uploaded to the Wellesley www server (using Fetch or WS_FTP) before you can view it. Make sure the script box is unchecked, and hit the "view page" button.

Learning JavaScript

Netscape maintains a manual describing everything you ever wanted to know (and more) about JavaScript 1.3 at:
http://developer.netscape.com/docs/manuals/js/client/
jsguide/index.htm
It's a pretty old document, but still useful.

After you've read that manual, you can instantly acquire years of experience and avoid code faux pas by reading "Javascript Best Practice":
http://www.irt.org/articles/js169/#4

For the less technically inclined, Dreamweaver writes scripts for you using what it calls "Behaviors". Use the behaviors dialog box to indicate what you want to happen at given events. It is also fairly common practice to trade scripts and credit the origin of the script within an HTML or JavaScript comment. The authors of a book on JavaScript maintain a companion web site so that you can copy their scripts:
http://www.chalcedony.com/javascript/

JavaScript and assorted interactive features are bundled together in an acronym: DHTML (dynamic HTML). Try a search for DHTML in a popular search engine and you'll have enough reading material for a lifetime.

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