+=head1 SUPPORT FOR JAVASCRIPT
+
+Netscape versions 2.0 and higher incorporate an interpreted language
+called JavaScript. Internet Explorer, 3.0 and higher, supports a
+closely-related dialect called JScript. JavaScript isn't the same as
+Java, and certainly isn't at all the same as Perl, which is a great
+pity. JavaScript allows you to programmatically change the contents of
+fill-out forms, create new windows, and pop up dialog box from within
+Netscape itself. From the point of view of CGI scripting, JavaScript
+is quite useful for validating fill-out forms prior to submitting
+them.
+
+You'll need to know JavaScript in order to use it. There are many good
+sources in bookstores and on the web.
+
+The usual way to use JavaScript is to define a set of functions in a
+<SCRIPT> block inside the HTML header and then to register event
+handlers in the various elements of the page. Events include such
+things as the mouse passing over a form element, a button being
+clicked, the contents of a text field changing, or a form being
+submitted. When an event occurs that involves an element that has
+registered an event handler, its associated JavaScript code gets
+called.
+
+The elements that can register event handlers include the <BODY> of an
+HTML document, hypertext links, all the various elements of a fill-out
+form, and the form itself. There are a large number of events, and
+each applies only to the elements for which it is relevant. Here is a
+partial list:
+
+=over 4
+
+=item B<onLoad>
+
+The browser is loading the current document. Valid in:
+
+ + The HTML <BODY> section only.
+
+=item B<onUnload>
+
+The browser is closing the current page or frame. Valid for:
+
+ + The HTML <BODY> section only.
+
+=item B<onSubmit>
+
+The user has pressed the submit button of a form. This event happens
+just before the form is submitted, and your function can return a
+value of false in order to abort the submission. Valid for:
+
+ + Forms only.
+
+=item B<onClick>
+
+The mouse has clicked on an item in a fill-out form. Valid for:
+
+ + Buttons (including submit, reset, and image buttons)
+ + Checkboxes
+ + Radio buttons
+
+=item B<onChange>
+
+The user has changed the contents of a field. Valid for:
+
+ + Text fields
+ + Text areas
+ + Password fields
+ + File fields
+ + Popup Menus
+ + Scrolling lists
+
+=item B<onFocus>
+
+The user has selected a field to work with. Valid for:
+
+ + Text fields
+ + Text areas
+ + Password fields
+ + File fields
+ + Popup Menus
+ + Scrolling lists
+
+=item B<onBlur>
+
+The user has deselected a field (gone to work somewhere else). Valid
+for:
+
+ + Text fields
+ + Text areas
+ + Password fields
+ + File fields
+ + Popup Menus
+ + Scrolling lists
+
+=item B<onSelect>
+
+The user has changed the part of a text field that is selected. Valid
+for:
+
+ + Text fields
+ + Text areas
+ + Password fields
+ + File fields
+
+=item B<onMouseOver>
+
+The mouse has moved over an element.
+
+ + Text fields
+ + Text areas
+ + Password fields
+ + File fields
+ + Popup Menus
+ + Scrolling lists
+
+=item B<onMouseOut>
+
+The mouse has moved off an element.
+
+ + Text fields
+ + Text areas
+ + Password fields
+ + File fields
+ + Popup Menus
+ + Scrolling lists
+
+=back
+
+In order to register a JavaScript event handler with an HTML element,
+just use the event name as a parameter when you call the corresponding
+CGI method. For example, to have your validateAge() JavaScript code
+executed every time the textfield named "age" changes, generate the
+field like this:
+
+ print textfield(-name=>'age',-onChange=>"validateAge(this)");
+
+This example assumes that you've already declared the validateAge()
+function by incorporating it into a <SCRIPT> block. The CGI.pm
+start_html() method provides a convenient way to create this section.
+
+Similarly, you can create a form that checks itself over for
+consistency and alerts the user if some essential value is missing by
+creating it this way:
+ print startform(-onSubmit=>"validateMe(this)");
+
+See the javascript.cgi script for a demonstration of how this all
+works.
+
+