Use for example Google Chrome developer tools, see: http://stackoverflow.com/questions/855126/what-is-the-best-way-to-profile-javascript-execution

It seems this has not been discussed a lot on programmers.SE but on stack exchange you can find a lot practical tools and methods to perform this task.

Generally Google Chrome is a good tool for it but off-course it is not cross browser. So, if performance in other browsers should be as good take a look on the specific tools for those browsers (look for profiler / performance profiler / etc).

There are also JS based tools (not sure how accurate they are since they measure from within the javascript engine):

http://code.google.com/p/jslitmus/

Use for example Google Chrome developer tools, see: https://stackoverflow.com/questions/855126/what-is-the-best-way-to-profile-javascript-execution

It seems this has not been discussed a lot on programmers.SE but on stack exchange you can find a lot practical tools and methods to perform this task.

Generally Google Chrome is a good tool for it but off-course it is not cross browser. So, if performance in other browsers should be as good take a look on the specific tools for those browsers (look for profiler / performance profiler / etc).

There are also JS based tools (not sure how accurate they are since they measure from within the javascript engine):

http://code.google.com/p/jslitmus/