Run results for: Object keys length vs for in

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Browser: Chrome 132

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Benchmark engine: Benchmark.js

for in

142.1M/s

Object keys

113.0M/s

View exact numbers

Test name	Executions per second
✓ for in	142,106,784 Ops/sec
Object keys	113,018,160 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 }