Run results for: for vs. for-in vs. for-of vs. reduce (map object values)

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36

Browser: Chrome 125

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Benchmark engine: Benchmark.js

for-in loop

1.0M/s

for-of loop

921K/s

for loop

920K/s

reduce

455K/s

View exact numbers

Test name	Executions per second
✓ for-in loop	1,015,701 Ops/sec
for-of loop	921,457 Ops/sec
for loop	919,528 Ops/sec
reduce	454,963 Ops/sec

Script Preparation code:

var source = {
  "box-sizing": "border-box",
  "margin": 0,
  "padding": 0,
  "border-width": 0,
  "border-style": "solid",
  "border-color": "#ddd"
}

function iteratee(value) {
  return `${value} !important`
}

Tests:

for loop
const sourceKeys = Object.keys(source) const result = {} for (let i = 0; i < sourceKeys.length; i++) { result[sourceKeys[i]] = iteratee(source[sourceKeys[i]]) }
for-in loop
const result = {} for (const key in source) { result[key] = iteratee(source[key]) }
for-of loop
const result = {} for (const key of Object.keys(source)) { result[key] = iteratee(source[key]) }
reduce
const result = Object.keys(source).reduce((memo, key) => { return { ...memo, [key]: iteratee(source[key]) } }, {})

Run results for: for vs. for-in vs. for-of vs. reduce (map object values)

Make a new object by applying a function to each value of the source object.

for loop

for-in loop

for-of loop

reduce