Results:

A: typeof obj == “object” : 439 msec
B: util.isObj(obj) : 1228 msec (where util = { isObj : function(o) { return typeof o == “object”; } })
C: isObj(obj) : 1155 msec (where B and isObj = util.isObj)

Conclusions:

First, remember that these are looping over 100 million iterations. This kind of research might be useful for a worker thread, but it’s not terribly useful for day to day stuff.

The big conclusion here is if you’re only going to call a function from one or two places, or it’s very short, skipping the function and putting the code inline will save you about 60%, but it’s really only significant if you’re calling that function millions of times.

The second conclusion is that if you must use a function for something like this (millions of calls), you can save a tiny bit—almost completely insignificant—of time by getting a reference to that function. Keep in mind that this micro-optimization only works if the function you’re calling doesn’t require context. If you have to use the .call or .apply methods to add context, this approach is actually about 17x slower.

Actual testing code at http://jsfiddle.net/jsylvanus/tTsXp/

The short version of the result is that the md5() function won across the board. The comments in the php.net hash function documentation seemed to indicate a performance increase in using hash(‘md5′,$str), and an even better increase in hash(‘md4′,$str). I found this to only partially be the case; While using the hash function, md4 is minutely faster than md5, the md5() function itself is considerably faster than either of these.

So, for any performance sensitive case, I would say md5() is by far the best choice.

Actual results of the test suite can be seen here: