Run results for: for-in vs for..of object.keys

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.1 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 15

Operating system: iOS 15.1

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
for-in	2.8 Ops/sec
Object.keys	2.3 Ops/sec
for..of Object.keys	2.6 Ops/sec

Script Preparation code:

var obj = {
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
    'h': 1,
    'i': 1,
    'j': 1,
    'k': 1,
    'l': 1,
    'm': 1,
    'n': 1,
    'o': 1,
    'p': 1,
    'q': 1,
    'r': 1,
    's': 1,
    't': 1,
    'u': 1,
    'v': 1,
    'w': 1,
    'x': 1,
    'y': 1,
    'z': 1,
};

Tests:

for-in
for (let i=10000; i > 0; i--) { for (const key in obj) { console.log(key); } }
Object.keys
for (let i=10000; i > 0; i--) { Object.keys(obj).forEach(key => console.log(key)); }
for..of Object.keys
for (let i=10000; i > 0; i--) { for (const key of Object.keys(obj)) { console.log(key); } }

Run results for: for-in vs for..of object.keys

for-in

Object.keys

for..of Object.keys