How to do performance analysis of a heavy JavaScript web app?

I have a huge Web App that's switching from a HTML-rendered-on-the-server-and-pushed-to-the-client approach to a let-the-client-decide-how-to-rend开发者_JAVA百科er-the-data-the-server-sends, which means the performance on the client mattered in the past, but it's critica now. So I'm wondering if in the current state of affairs it's possible to profile Web apps and extract the same data (like call stacks, "threads", event handlers, number of calls to certain functions, etc) we use for server side perf.

I know every browser implements some of these functionalities to some extent (IE dev tools has an embedded profiler, so does Firefox [with Firebug], and Google Chrome has Speed Tracer), but I was wondering if it'd be possible to get, for example, stack traces of sessions. Is it advisable to instrument the code and have a knob to turn on/off the instrumentation? Or it's simply not that useful to go that level in analyzing JavaScript performance?

Fireunit is decent and YUI also provides a profiler, but neither provide stack traces or call frames. Unfortunately, there aren't many JS profiling tools out right now. And none of them are particularly great.

I think it's very important to go to a high level of performance analysis, especially considering the user will deal with the JS app 90%+ of the time directly.