Run results for: For in vs Object.keys.forEach

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Safari/537.36

Browser: Chrome 72

Operating system: Mac OS X 10.14.2

Device Platform: Desktop

Date tested: 5 years ago

Test name	Executions per second
For In	1005.3 Ops/sec
Object keys forEach	977.5 Ops/sec

Script Preparation code:

var obj = new Object()
var keys = (new Array(100)).fill(0).map((x, i) => { return i + 1 })
keys.forEach((x) => { obj['prop' + x] = x })

Tests:

For In
for (var key in obj) { if (obj.hasOwnProperty(key)) console.log(obj[key]) }
Object keys forEach
Object.keys(obj).forEach(key => console.log(obj[key]))