Which JS benchmark site is correct?

Question

I created a benchmark on both jsperf.com and jsben.ch, however, they\'re giving substantially different results.

JSPerf: https://jsperf.com/join-vs-template-venryx

Answer 1

AFAIK one issue is that various JavaScript engines optimize vastly differently based on the environment.

I have a test of the exact same function that produces different results based on where the function is created. In other words, for example, in one test it's

const lib = {}
lib.testFn = function() {
   ....
}

And in other it's

const lib = {
 testFn: function() {
   ....
 },
};

and in another it's

function testFn() {
   ....
}

const lib = {}
lib.testFn = testFn

and there's a >10% difference in results for a non-trivial function in the same browser and different results across browsers.

What this means is no JavaScript benchmark is correct because how that benchmark runs it's tests, as in the test harness itself, affects the results. The harness for example might XHR the test script. Might call eval. Might run the test in a worker. Might run the test in an iframe. And the JS engine might optimize all of those differently.