The IE9 Platform Preview includes the first release of the new JavaScript engine. This new engine compiles JavaScript source code into high-quality native machine code. It also has a new fast interpreter for sequentially executing script on traditional web pages and contains several improvements to the JavaScript runtime (including improvements in type representation, polymorphic inline caching and efficient implementation of machine types).  IE 9’s JS engine employs a dual execution pipeline architecture which enables very efficient interpreting of JS code while at the same time compiling JS code in the background (on a different thread), taking advantage of the processing power of modern hardware.  In terms of code analysis, IE 9's JS engine analyzes hot functions and puts them into a queue for background compilation. There are other types of analysis that happen (or could happen). For example, the ability to change execution strategies based on power state (if a PC is on battery power, for example, then limit the amount of codegen).  In this episode of Going Deep, we meet the leaders of the team that builds this new high performance JavaScript engine: GM Shanku Niyogi, Architect Steve Lucco and GPM John Montgomery. If you're interested in how IE 9's JavaScript engine works, then you'll certainly enjoy this great conversation. Tune in. Enjoy.