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

Test name	Executions per second
✓ Native Event listener with callbacks array	49,503 Ops/sec
Custom EventTarget with callbacks array	47,109 Ops/sec
Fake listeners array	23,954 Ops/sec
Custom EventTarget	743 Ops/sec
Native Event listeners	664 Ops/sec

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]();