Run results for: Object.keys vs for-in

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.4 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 15

Operating system: iOS 15.4

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
Object.keys	44.2 Ops/sec
for-in with var	52.0 Ops/sec
for-in with let	52.1 Ops/sec

Script Preparation code:

var obj = {
    'a': 1,
    'b': 2,
    'c': 3,
    'd': 4,
    'e': 5,
    'f': 6,
    'g': 7,
    'h': 8,
    'i': 9,
    'j': 10,
    'k': 11,
    'l': 12,
    'm': 13,
    'n': 14,
    'o': 15,
    'p': 16,
    'q': 17,
    'r': 18,
    's': 19,
    't': 20,
    'u': 21,
    'v': 22,
    'w': 23,
    'x': 24,
    'y': 25,
    'z': 26
};

Tests:

Object.keys
for (var i = 0; i < 1000; i++) { Object.keys(obj).forEach(key => console.log(key)); }
for-in with var
for (var i = 0; i < 1000; i++) { for (var key in obj) { console.log(key); } }
for-in with let
for (let i = 0; i < 1000; i++) { for (let key in obj) { console.log(key); } }

Run results for: Object.keys vs for-in

Object.keys

for-in with var

for-in with let