Run results for: Object.keys(obj)[0] vs for in

Run details:

User agent: Mozilla/5.0 (Linux; Android 7.0; LG-M400) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.101 Mobile Safari/537.36

Browser: Chrome Mobile 87

Operating system: Android 7.0

Device Platform: Mobile

Date tested: 3 years ago

Test name	Executions per second
for-in	137.3 Ops/sec
Object.keys	49.1 Ops/sec

Script Preparation code:

var obj = {'a': 1}

Tests:

for-in
for (var i=10000; i > 0; i--) { let first for (let key in obj) { first = key break } }
Object.keys
for (var i=10000; i > 0; i--) { const first = Object.keys(obj)[0] }