Run results for: Array.includes() vs Set.has() for small Arrays invoked many times

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Browser: Chrome 132

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

Array.includes, 20 elements

21.8M/s

Set.has, 20 elements

19.6M/s

Array to Set + Set.has, 10 000 elements

3.2M/s

Array to Set + Set.has x 1000, 20 elements

42K/s

Array.includes x 1000, 20 elements

25K/s

View exact numbers

Test name	Executions per second
✓ Array.includes, 20 elements	21,788,200 Ops/sec
Set.has, 20 elements	19,631,472 Ops/sec
Array to Set + Set.has, 10 000 elements	3,161,618 Ops/sec
Array to Set + Set.has x 1000, 20 elements	41,770 Ops/sec
Array.includes x 1000, 20 elements	24,532 Ops/sec

Script Preparation code:

function getArray(length) {
  const result = [];
  for (let i = 0; i < length; i++) {
    result.push(i + 'abc'); // In case the browser does some sort of optimization for arrays with only integers ¯\_(ツ)_/¯
  }
  return result;
}

function getRandomTargetElement(arrayLength) {
  const index = Math.floor(Math.random() * arrayLength);
  return index + 'abc';
}


array_small = getArray(20);

set_small = new Set(array_small);

Tests:

Array.includes, 20 elements
array_small.includes(getRandomTargetElement(20));
Set.has, 20 elements
set_small.has(getRandomTargetElement(20))
Array to Set + Set.has, 10 000 elements
const target = getRandomTargetElement(10000); const set = new Set(array_small); set.has(target)
Array to Set + Set.has x 1000, 20 elements
const set = new Set(array_small); for (let i = 0; i < 1000; i++) { const target = getRandomTargetElement(20); set.has(target) }
Array.includes x 1000, 20 elements
for (let i = 0; i < 1000; i++) { const target = getRandomTargetElement(20); array_small.includes(target) }