Microsoft has released what it calls a "power tool" for  measuring performance of portions of Web applications executing JavaScript inside a browser. 

Visual Studio 2008 AJAX Profiling Extensions is an add-on to performance tools available in Visual Studio Team System 2008 Development Edition and Visual Studio Team Suite, said S. "Soma" Somasegar, senior vice president of the Microsoft Developer Division, in a blog entry. Developers can profile client-side JavaScript code.

"The AJAX Profiling Extensions provide much-needed visibility into often complex, Web client-side interactions for the first time," Somasegar said. "You do not need to download and install any additional software, plug-ins, or ActiveX controls on the machine where the AJAX web client code is running to use the AJAX Profiling Extensions to gather JavaScript execution-time data. Also, this works with any web browser, including, of course, the latest version of Internet Explorer."

The extensions, accessible at this web page, rewrite JavaScript functions enabling instrumentation to measure and log performance data. This data is periodically uploaded from the client browser to the Internet Information Services Web Server.