Run results for: Object keys length vs for in

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
Object keys	11718334.0 Ops/sec
for in	31225580.0 Ops/sec

Script Preparation code:

var create = 60000;
var myMap = {}
var objectToCopy = {
    myUrl: 'test',
    someUrl: 'test/11',
    otherProp: true
}

for (let i; i < create; i++) {
    myMap[i] = {
        ...objectToCopy
    }
}

Tests:

Object keys
if (Object.keys(myMap).length) { // do something }
for in
let hasProp = false; for (const prop in myMap) { hasProp = true; break; } if (hasProp) { // do something }