1. The Web Wizard’s Guide to Freeware/Shareware Chapter Five Scripts and Applets

2. Chapter Objectives To understand the different between JavaScript programs and Java applets, and find out where to find free ones on the Web To learn how to install a simple JavaScript script on a Web page To see how JavaScript is used to handle hot zones on a Web page To find out how to install a simple applet on a Web page To see how sophisticated applets can display all kinds of data

3. Scripts and Applets Scripts are inserted into a Web page using a programming language named JavaScript. Applets are inserted into a Web page by specifying the name of a file that contains code written in a programming language named Java. You don’t need to be a programmer to add scripts and applets to your Web pages.

4. JavaScript Scripts Some scripts are browser-dependent. Always check for comments about browser compatibility: whenever possible, select scripts that work for both IE and Netscape Navigator. Scripts are usually distributed as cut-and-paste text files – you have to insert them into your.html files and modify appropriate settings by hand. Look for simple scripts with easy-to-understand documentation when you are first trying to get off the ground.

5. Java Applets Applets come packaged in binary.class files that cannot be edited or altered. Some applets require a some customization settings, but applets are generally easier to install than scripts. You don’t need to know any Java in order to install a Java applet.

6. What Are the Risks? Scripts can examine files on your hard drive and send information out over the Internet: scripts therefore entail some risk to your privacy online (e.g. cookies are added to Web pages with scripts). Malicious scripts can be written, but are not likely to show up at a reputable clearinghouse. Applets cannot read from files on your computer or write to files, so applets do not pose any security or privacy risks (unless you volunteer information to the applet by interacting with it).

7. Special-Effects Scripts Animations and other special effects can be added to Web pages with scripts (e.g. PicturePong). Examine comment lines (lines that start with //) to see where you can insert your own customized settings. Some longer scripts are stored in.js files – these are just text files that you can edit just like cut-and-paste text snippets.

8. Mouseover Scripts If you want to see special effects when users roll their mouse over a navigation panel, or other hot zones, you need a mouseover script. One script can be used for all your mouseover pages, but you’ll have to customize it to work with different button sets and graphics files. A simple mouseover script is given in the text (see Fig. 5.3)

9. Special-Effects Applets Special visual effects can be added to your.jpg and.gif images with applets (e.g. the falling snow alcsnow applet). Other applets support user interactions (e.g. the image morphing AlexWarp applet). You can find many surprising (and free!) special effects for your Web pages in applet archives.

10. Workhorse Applets Some applets support data-driven displays which make it easier to post breaking news and announcements on your Web pages. Other applets make it possible for multiple users to interact over the Web (e.g. chat rooms with shared white boards).