Run results for: cost of eventListeners

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.3.1 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 18

Operating system: iOS 18.3.2

Device Platform: Mobile

Date tested: one year ago

Test name	Executions per second
running async 1000 event listeners	5.6 Ops/sec
running async 501 event listeners	2.0 Ops/sec

Script Preparation code:

var audio = document.createElement("audio");

function andAOne(e){ 
  e.count = (e.count|| 0) +1; 
}

function andAOneAndAStop(e){ 
  e.count = (e.count|| 0) +1; 
  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",andAOneAndAStop.bind({})); audio.playbackRate = 2;

Run results for: cost of eventListeners

meassuring the cost of just calling an event listener.

running async 1000 event listeners

running async 501 event listeners