Benchmark: map/forEach arrow/function VS for let/var VS for const/let/var of

Script Preparation code:

var arr = [...Array(10000).keys()];
var a;

Tests:

map arrow
a = 0; arr.map(x => { a += x + 2; }) console.log(a);
map function
a = 0; arr.map(function(x) { a += x + 2; }) console.log(a);
forEach arrow
a = 0; arr.forEach(x => { a += x + 2; }) console.log(a);
forEach function
a = 0; arr.forEach(function(x) { a += x + 2; }) console.log(a);
for let
a = 0; for (let i = 0; i < 10000; i++) { a += arr[i] + 2; } console.log(a);
for var
a = 0; for (var i = 0; i < 10000; i++) { a += arr[i] + 2; } console.log(a);
for const of
a = 0; for (const x of arr) { a += x + 2; } console.log(a);
for let of
a = 0; for (let x of arr) { a += x + 2; } console.log(a);
for var of
a = 0; for (var x of arr) { a += x + 2; } console.log(a);

Rendered benchmark preparation results:

Previous results

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Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:99.0) Gecko/20100101 Firefox/99.0

Browser/OS: Firefox 99 on Mac OS X 10.15

map/forEach arrow/function VS for let/var VS for const/let/var of (version: 0)