Run results for: the cost of eventListeners

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.125 Safari/537.36

Browser: Chrome 84

Operating system: Linux

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
running async 1000 event listeners	2.4 Ops/sec
running async 501 event listeners	0.8 Ops/sec

Script Preparation code:

var audio = document.createElement("audio");

function andAOne(e){ 
  e.count = (e.count|| 0) +1; 
}

function stop501(e){ 
  e.count === 501 && e.stopPropagationImmediately();
}

Tests:

running async 1000 event listeners
for (var i = 0; i <1000; i++) audio.addEventListener("ratechange",andAOne.bind({})); audio.playbackRate = 2;
running async 501 event listeners
for (var i = 0; i <1000; i++) audio.addEventListener("ratechange",andAOne.bind({})); audio.addEventListener("ratechange",stop501); audio.playbackRate = 2;

Run results for: the cost of eventListeners

meassuring the cost of just calling an event listener.

running async 1000 event listeners

running async 501 event listeners