Benchmark.options.onStart and onComplete are called multiple times per Benchmark run about benchmark.js

[EliSnow]

Upon further examination this appears to be a difference between Benchmark.prototype.onStart and benchmark.events.start. Why the difference? I would assume that using onStart verses on("start",...) would net the same affect.

[jdalton]

Internally the benchmark is cloned to collect a sample of runs, by setting the Benchmark.options.onStart you're adding that as the default onStart for all benchmarks created (even the internal clones).

[EliSnow]

While I understand what is going on internally with cloned benchmarks, the difference in behavior between benchmark.onStart and adding an event listener with benchmark.on("start", ...) seems unintuitive. The confusion arises because I am used to the DOM event model where DOMElement.onClick = ... and DOMElement.addEventListener("click", ... behave the same.

[jdalton]

Benchmark.options is the default options for all benchmarks created. The Benchmark constructor accepts an options object where onStart can be specified or later on the benchmark instance via myBench.on('start', ...).

[EliSnow]

Thank you for the clarification. It seems onStart should never be directly set on a benchmark object. Correct me if I'm wrong @jdalton, but when a benchmark is cloned the original benchmark itself acts as the options object during the construction of the clone.

If I may ask one more rhetorical question, would it not make sense that clones created internally during run have their events cleared? I say this because benchmark.onStart benchmark.onCycle and benchmark.onComplete should accomplish everything needed.

[jdalton]

There is no mybench.onStart, or mybench.onCycle or mybench.onComplete. There are options properties for onStart, onCycle and the rest. The clones are created with their event listeners mandated to them.