Run results for: Performance of JavaScript .forEach vs for in

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:135.0) Gecko/20100101 Firefox/135.0

Browser: Firefox 135

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Object.entries()

667/s

for in

570/s

for in with variable

557/s

View exact numbers

Script Preparation code:

function generateTestObject() {
  const result = {};
  for (let i = 0; i < 10000; ++i) {
    result['v'+i] = i
  }
  return result;
}

Tests:

Object.entries()
const object = generateTestObject(); Object.entries(object).forEach(([key, value]) => { const test = key + '' + value })
for in
const object = generateTestObject(); for(key in object){ const test = key + '' + object[key] }
for in with variable
const object = generateTestObject(); for(key in object){ const value = object[key] const test = key + '' + value }