Run results for: Object copy loop compare

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:89.0) Gecko/20100101 Firefox/89.0

Browser: Firefox 89

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
for-in	170.9 Ops/sec
Object.keys.forEach	149.7 Ops/sec
Object.entries.forEach	71.2 Ops/sec
Object.keys for	123.7 Ops/sec

Script Preparation code:

const hasOwnProperty = Object.prototype.hasOwnProperty
function has (obj, key) { return hasOwnProperty.call(obj, key) }
const count = 10000
function loop (fn) { for (let i = count; i > 0; i--) fn() }
var obj = { a: 1, b: 1, c: 1, d: 1, e: 1, f: 1, g: 1 }
var result = {}

Tests:

for-in
loop(function () { for (const key in obj) { if (has(obj, key)) result[key] = obj[key] } })
Object.keys.forEach
loop(function () { Object.keys(obj).forEach(function (key) { result[key] = obj[key] }) })
Object.entries.forEach
loop(function () { Object.entries(obj).forEach(function ([key, value]) { result[key] = value }) })
Object.keys for
loop(function () { const keys = Object.keys(obj) const length = keys.length for (let i = length; i > 0; i--) { const key = keys[i] result[key] = obj[key] } })

Run results for: Object copy loop compare

for-in

Object.keys.forEach

Object.entries.forEach

Object.keys for