ASP.NET 2.0 All-In-One Desk Reference For Dummies®

Chapter 5. Using Client-Side Script

In This Chapter

✓	Peering into Microsoft.com’s use of browser script
✓	Inserting client-side script using server code
✓	Warnings and confirmations
✓	Validating with client-side script
✓	Refreshing part of a page using callbacks

Client-side scripting refers to a program that runs inside the browser page rather than on the Web server. One of the oldest uses of client-side script is rollover effects on HTML buttons. When the mouse passes over an image, the browser raises an event flag. A handler executes a tiny piece of code that points to a different image than the one originally displayed. The second image usually has a slightly different appearance.

By running code inside the browser, you can harness the local computer’s horsepower and bypass the page refreshes that slow down server-side applications. Reloading everything that appears on a page just to validate whether the user enters a value in a text box doesn’t make much sense. If you use enough client-side script, a browser page can give you the responsiveness of a typical Windows forms program while keeping the advantage of easy code updates on the server.

ASP.NET 2.0 uses client-side scripting extensively. That may sound odd for a server-side programming technology, but it makes sense. Server-side code can deliver custom markup to each user’s browser. Included in that individual markup, you can find content that generates custom client-side script. As you can see in this chapter, architects are working ...