What is the best way to profile javascript execution?

Question

Is there a good profiler for javascript? I know that firebug has some support for profiling code. But I want to determine stats on a longer scale. Imagine you are building a lot of javascript code and you want to determine what are actually the bottlenecks in the code. At first I want to see profile stats of every javascript function and execution time. Next would be including DOM functions. This combined with actions that slows things down like operation on the rendering tree would be perfect. I think this would give a good impression if the performance is killed in my code, in DOM preparation or in updates to the rendering tree/visual.

Is there something close to what I want? Or what would be the best tool to achieve the most of what I've described? Would it be a self compiled browser plus javascript engine enhanced by profile functionality?

Answer 1

Firebug provides a highly detailed profiling report. It will tell you how long each method invocation takes in a giant (detailed) table.

console.profile([title])
//also see
console.trace()

Blackbird also has a simpler profiler.

Answer 2

Firebug+Firefox is a must have. And IE 8's developer toolbar also has a profiler built in (IE 8 ships with the developer toolbar).

Answer 3

Safari 4's web inspector also includes a profiler (although the version in the nightlies is improved wrt. recursive function calls). The Web Inspector also supports Firebug's profiler APIs.

Answer 4

Although Firebug has been mentioned, one additional thing you would want to look at with Firebug is a plugin for Firebug called FireUnit; John Resig talks about it in this blog post:

JavaScript Function Call Profiling

Hope that helps.

Answer 5

For JavaScript, XmlHttpRequest, DOM Access, Rendering Times and Network traffic for IE6, 7 & 8 you can use the FREEdynaTrace AJAX Edition