Run results for: Event Listener Performance

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0

Browser: Firefox 84

Operating system: Windows

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
Default Event	160.9 Ops/sec
Passive Event	158.0 Ops/sec

Script Preparation code:

function calculatePrimes(iterations, multiplier) {
  var primes = [];
  for (var i = 0; i < iterations; i++) {
    var candidate = i * (multiplier * Math.random());
    var isPrime = true;
    for (var c = 2; c <= Math.sqrt(candidate); ++c) {
      if (candidate % c === 0) {
          // not prime
          isPrime = false;
          break;
       }
    }
    if (isPrime) {
      primes.push(candidate);
    }
  }
  return primes;
}

Tests:

Default Event
window.bus1 = window.document.createElement('main'); window.bus1.addEventListener('test1', (event) => { var primes = calculatePrimes(10, 1000000000); }); const event1 = new CustomEvent('test1'); if (window.bus1.dispatchEvent(event1)) { console.log('1'); }
Passive Event
window.bus2 = window.document.createElement('main'); window.bus2.addEventListener('test2', async (event) => { new Promise(() => { var primes = calculatePrimes(10, 1000000000) }); }, {passive: true}); const event2 = new CustomEvent('test2', { cancelable: false, }); if (window.bus2.dispatchEvent(event2)) { console.log('2'); }

Run results for: Event Listener Performance

Default Event

Passive Event