Run results for: operator `in` vs. get property by key

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser: Chrome 121

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
if (key in obj)	2.9 Ops/sec
if (object[key])	2.8 Ops/sec

Script Preparation code:

var list = Array.from({ length: 1_000_000 }, _ => crypto.randomUUID());
var object = Object.create(null);

var x;

list.toReversed().forEach((i, idx) => {
	if (idx % 2) {
		object[i] = [0x1];
	}
});

Tests:

if (key in obj)
list.forEach((key) => { if (key in object) { x = object[key]; } });
if (object[key])
list.forEach((key) => { if (object[key]) { x = object[key]; } });

Run results for: operator `in` vs. get property by key

if (key in obj)

if (object[key])