Run results for: for..in or keys+forEach

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Firefox/52.0

Browser: Firefox 52

Operating system: Mac OS X 10.12

Device Platform: Other

Date tested: 7 years ago

Test name	Executions per second
for..in	21967.5 Ops/sec
keys+forEach	11397.7 Ops/sec

Script Preparation code:

testObj = {};
for(let i = 0; i < 1000; i++) {
  testObj['a'+i] = i;
}

Tests:

for..in
let acc = 0; for (let k in testObj) { acc += testObj[k]; }
keys+forEach
let acc = 0; Object.keys(testObj).forEach((k) => { acc += testObj[k]; });