Run results for: for vs. for-in vs. for-of vs. map vs. reduce (map object entries then join)

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.67 Safari/537.36

Browser: Chrome 101

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
for loop (without join)	239246.7 Ops/sec
for loop (with join)	190983.2 Ops/sec
for-in loop	215043.9 Ops/sec
for-of loop	176038.4 Ops/sec
map	323242.6 Ops/sec
reduce	296104.9 Ops/sec

Script Preparation code:

var source = {
  "box-sizing": "border-box",
  "margin": 0,
  "padding": 0,
  "border-width": 0,
  "border-style": "solid",
  "border-color": "#ddd",
  "letter-spacing": "calc(0.04 * (1rem - 1em))",
  "transition-property": "none",
  "transition-duration": "0.3s"
}

function iteratee(property, value) {
  return `${property}:${value}`
}

Tests:

for loop (without join)
const sourceKeys = Object.keys(source) let result = "" for (let i = 0; i < sourceKeys.length; i++) { result += iteratee(sourceKeys[i], source[sourceKeys[i]]) if (i < sourceKeys.length - 1) { result += ";" } }
for loop (with join)
const sourceKeys = Object.keys(source) const resultArray = new Array(sourceKeys.length) for (let i = 0; i < sourceKeys.length; i++) { resultArray[i] = iteratee(sourceKeys[i], source[sourceKeys[i]]) } const result = resultArray.join(";")
for-in loop
const resultArray = [] for (const key in source) { resultArray.push(iteratee(key, source[key])) } const result = resultArray.join(";")
for-of loop
const resultArray = [] for (const key of Object.keys(source)) { resultArray.push(iteratee(key, source[key])) } const result = resultArray.join(";")
map
const result = Object.keys(source) .map((key) => `${key}:${source[key]}`) .join(";")
reduce
const result = Object.keys(source).reduce((memo, key) => { const mapResult = iteratee(key, source[key]) return (memo) ? `${memo};${mapResult}` : mapResult })

Run results for: for vs. for-in vs. for-of vs. map vs. reduce (map object entries then join)

Apply a function to each key-value pair in the source object, then join the results into a string.

for loop (without join)

for loop (with join)

for-in loop

for-of loop

map

reduce