Benchmark: Performance of JavaScript .forEach, .map and .reduce vs for and for..of2

Script Preparation code:

function generateTestArray() {
  const result = [];
  for (let i = 0; i < 1000000; ++i) {
    result.push({
      a: i,
      b: i / 2,
      r: 0,
    });
  }
  return result;
}
var array = generateTestArray();

Tests:

.forEach
array.forEach((x) => { x.r = x.a + x.b; });
for..of
for(const x of array) { x.r = x.a + x.b; }
for..of (destructuring)
const r = []; for(const {a, b} of array) { r.push(a + b); }
.map
array.map(x => x.a + x.b)
.map (destructuring)
array.map(({a,b}) => a + b)
.for (init array)
const r = new Array(array.length); for (let i = 0; i < array.length; ++i) { r[i] = array[i].a + array[i].b; }
.reduce
array.reduce((p, x) => p + x.a + x.b, 0);
.reduce (destructuring)
array.reduce((p, {a,b}) => p + a + b, 0);
for..of (reduce)
let r = 0; for (const x of array) { r += x.a + x.b; }
for..of (reduce) (destructuring)
let r = 0; for (const {a,b} of array) { r += a + b; }
forEach index
array.forEach((_, i) => { array[i].r = array[i].a + array[i].b; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.forEach
for..of
for..of (destructuring)
.map
.map (destructuring)
.for (init array)
.reduce
.reduce (destructuring)
for..of (reduce)
for..of (reduce) (destructuring)
forEach index

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36

Browser/OS: Chrome 117 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
.forEach	75.9 Ops/sec
for..of	76.2 Ops/sec
for..of (destructuring)	27.3 Ops/sec
.map	23.1 Ops/sec
.map (destructuring)	21.6 Ops/sec
.for (init array)	6.6 Ops/sec
.reduce	64.2 Ops/sec
.reduce (destructuring)	69.2 Ops/sec
for..of (reduce)	77.3 Ops/sec
for..of (reduce) (destructuring)	77.2 Ops/sec
forEach index	6.4 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

Related benchmarks:

Performance of JavaScript .forEach, .map and .reduce vs for and for..of2 (version: 0)

Comparing performance of: .forEach vs for..of vs for..of (destructuring) vs .map vs .map (destructuring) vs .for (init array) vs .reduce vs .reduce (destructuring) vs for..of (reduce) vs for..of (reduce) (destructuring) vs forEach index

Created: one year ago by: Guest

Jump to the latest result

.forEach

for..of

for..of (destructuring)

.map

.map (destructuring)

.for (init array)

.reduce

.reduce (destructuring)

for..of (reduce)

for..of (reduce) (destructuring)

forEach index

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):