Run results for: Native Event listener vs custom EventTarget vs fake listeners array

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.198 Safari/537.36

Browser: Chrome 86

Operating system: Windows

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
Native Event listeners	188.6 Ops/sec
Native Event listener with callbacks array	5649.5 Ops/sec
Custom EventTarget	226.3 Ops/sec
Custom EventTarget with callbacks array	5645.6 Ops/sec
Fake listeners array	32414.0 Ops/sec

Tests:

Native Event listeners
let i = 1001; const results = []; while (--i) { const index = i; window.addEventListener('custom:test', () => { results.push('Native Event listener ' + index); }, {once: true}); } window.dispatchEvent(new CustomEvent('custom:test', {bubbles: false}));
Native Event listener with callbacks array
let i = 1001; const callbacks = []; const results = []; while (--i) { const index = i; callbacks.push(() => { results.push('Fake listeners array ' + index); }); } window.addEventListener('custom:test', () => { results.push('Native Event listener ' + index); let i = callbacks.length; while (--i) callbacks[i](); }, {once: true}); window.dispatchEvent(new CustomEvent('custom:test', {bubbles: false}));
Custom EventTarget
let i = 1001; const target = new EventTarget(); const results = []; while (--i) { const index = i; target.addEventListener('custom:test', () => { results.push('Custom EventTarget ' + index); }, {once: true}); } target.dispatchEvent(new CustomEvent('custom:test', {bubbles: false}));
Custom EventTarget with callbacks array
let i = 1001; const callbacks = []; const target = new EventTarget(); const results = []; while (--i) { const index = i; callbacks.push(() => { results.push('Fake listeners array ' + index); }); } target.addEventListener('custom:test', () => { results.push('Native Event listener ' + index); let i = callbacks.length; while (--i) callbacks[i](); }, {once: true}); target.dispatchEvent(new CustomEvent('custom:test', {bubbles: false}));
Fake listeners array
let i = 1001; const callbacks = []; const results = []; while (--i) { const index = i; callbacks.push(() => { results.push('Fake listeners array ' + index); }); } i = callbacks.length; while (--i) callbacks[i]();

Run results for: Native Event listener vs custom EventTarget vs fake listeners array

Native Event listeners

Native Event listener with callbacks array

Custom EventTarget

Custom EventTarget with callbacks array

Fake listeners array