Run results for: Object loops: for...in vs Object.keys+forEach (ES5) vs for...of (ES6) vs Object.entries (ES8)

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.4 Safari/605.1.15

Browser: Safari 18

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: one year ago

for...in

508K/s

for...of - values (ES6)

119K/s

Object.keys+forEach (ES5)

78K/s

for...of - keys (ES6)

78K/s

Object.entries (ES8)

31K/s

for...of - entries (ES8)

29K/s

View exact numbers

Script Preparation code:

var obj = {};
for (let i = 0; i < 1000; i++) {
  obj['abc_' + i] = i;
}

function foo(bar) {
  return bar * 2 * 2;
}

Tests:

for...in
for (const key in obj) { if (obj.hasOwnProperty(key)) foo(obj[key]); }
Object.keys+forEach (ES5)
Object.keys(obj).forEach(function(key) { foo(obj[key]); });
for...of - keys (ES6)
for (const key of Object.keys(obj)) { foo(obj[key]); }
for...of - values (ES6)
for (const value of Object.values(obj)) { foo(value); }
for...of - entries (ES8)
for (const [key, value] of Object.entries(obj)) { foo(value); }
Object.entries (ES8)
Object.entries(obj).forEach(function(key, value) { foo(value); });