I consider javascript the language of last resort. The browser compatibility and security issues associated with it can make it the most complex part of a page. For this reason, I strive to deliver pages to the browser ready for display. This isn’t always possible.

javascript is a vital part of web development, and I use it alot, but carefully. The following list describes some of the most common uses of javascript:

• Alert boxes (usually just debugging)
• Confirm boxes - great for ‘Are you sure … ‘ processing
• Detection of form inputs changed to ensure user doesn’t lose changes
• Changing state of buttons and inputs to disabled/readonly and back again
• Changing status displays, like colors or text on the page
• Opening new windows (window.open), often used for help and … Easter Eggs :)
• Timers (see post about Ladybug)
• Google (and other) Map APIs - these are cool http://code.google.com/apis/maps/documentation/
• Hiding content / menuing, using style.display="block/inline/none”
• Client-side validation and assisting the user in correcting errors, must revalidate on on server-side
• Page level validation - Ensuring that inputs are not only valid, but valid with respect to each other - for example if the status is ‘extended absence’, a return date must be specified. As mentioned about, server-side validation must also be performed.
• RIAs (Rich Internet Applications) - Sophisticated interfaces. These are usually based off javascript libraries & kits like dojo. Fundamental javascript skills are vital to work with the toolkits.
• Control of players - like Windows Media player and Flash
• Browser-specific page adjustments that can’t be done on the server-side
• Used to add things like Google analytics, support external data collection systems http://www.google.com/analytics/, also Google ads
• Choosing different .CSS files - often used to assist visually impaired site visitors with text size or color choices
• AJAX
• Input interaction - For example, if one input is chosen, another may be presented or set to a specific value