Run results for: for..in vs for loop with Object.keys

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Browser: Chrome 108

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
for-in	26.5 Ops/sec
for keys	31.8 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,
  'aa': 1,
  'ba': 1,
  'ca': 1,
  'da': 1,
  'ea': 1,
  'fa': 1,
  'ga': 1,
  'ha': 1,
  'ia': 1,
  'ja': 1,
  'ka': 1,
  'la': 1,
  'ma': 1,
  'na': 1,
  'oa': 1,
  'pa': 1,
  'qa': 1,
  'ra': 1,
  'sa': 1,
  'ta': 1,
  'ua': 1,
  'va': 1,
  'wa': 1,
  'xa': 1,
  'ya': 1,
  'za': 1,
  'ab': 1,
  'bb': 1,
  'cb': 1,
  'db': 1,
  'eb': 1,
  'fb': 1,
  'gb': 1,
  'hb': 1,
  'ib': 1,
  'jb': 1,
  'kb': 1,
  'lb': 1,
  'mb': 1,
  'nb': 1,
  'ob': 1,
  'pb': 1,
  'qb': 1,
  'rb': 1,
  'sb': 1,
  'tb': 1,
  'ub': 1,
  'vb': 1,
  'wb': 1,
  'xb': 1,
  'yb': 1,
  'zb': 1
};

Tests:

for-in
for (let i=100; i > 0; i--) { for (const key in obj) { console.log(key); } }
for keys
var keys = Object.keys(obj); for (let i=100; i > 0; i--) { for (let j = 0; j < keys.length; j ++) { console.log(keys[j]); } }

Run results for: for..in vs for loop with Object.keys

for-in

for keys