Obsolete - This page has been moved to the Dojo Book.

Profiling

Profiling is the term for looking at where time is spent by any Javascript code. If you have a problem with code taking too long, then it helps to use a profiling tool to diagnose exactly where all the time is being used.

When using some profiling tools you may need to use debugAtAllCosts and not a packaged version of dojo (see DebuggingJavascript). Using debugAtAllCosts will enable the profiling tool to allocate time spent per function to the correct source file -- otherwise you will end up with the elapsed times being allocated to anonymous functions which will make it difficult for you to understand!

Also make sure you have used any relevant PerformanceTuning techniques before you start profiling.

Profiling Tools

dojo.profile

dojo.profile is a package that implements timing primitives for recording how much time is spent in particular functions. To learn how to use it, the best resource is to search the tests directory and look at how it is used by various tests.

Venkman (for Firefox)

Free but a bit buggy to use. I have found it easiest to get into debugging mode with Venkman by using a debugger keyword in your sourcecode. Run the Venkman debugger, then run your code and it will stop at the breakpoint.

Venkman contains a profiling tool, although the reports are a bit difficult to use. It does work.

Tito web studio

It seems it does not work with Dojo. It modifies javascript, and obviously in some manner incompatible with Dojo.

Manually do it yourself

Get now at the start and end of a routine, and calculate the difference. Not a great technique, because you have to make educated guesses as to where the inefficient areas are, and it may take quite a lot of work to home in on the problem area.

But it is easy to do if you are measuring a single function:
    function() {
        var startTime = new Date();
        // do something here
        dojo.debug("Total time: " + (new Date() - startTime));
    }
 
Or another example of code to do this is on this page near the top under the heading "Measure your changes".