Run results for: Object keys length vs for in

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 16_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.1 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 16

Operating system: iOS 16.1.1

Device Platform: Mobile

Date tested: 2 years ago

Benchmark engine: Benchmark.js

for in

15.1M/s

Object keys

6.0M/s

View exact numbers

Test name	Executions per second
✓ for in	15,094,010 Ops/sec
Object keys	6,006,444 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 }