Run results for: Array iter vs set iter

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/93.0.4577.82 Safari/537.36

Browser: Chrome 93

Operating system: Windows

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
for of arr: few items	13616963.0 Ops/sec
for of set: few items	12446554.0 Ops/sec
native loop arr: few items	3632143.0 Ops/sec
native iter set: few items	13155265.0 Ops/sec
for of arr: many items	864121.4 Ops/sec
for of set: many items	541747.8 Ops/sec
native loop arr: many items	15825.5 Ops/sec
native iter set: many items	564363.7 Ops/sec

Script Preparation code:

var fewItemArr = [1, 2, 3];
var fewItemSet = new Set(fewItemArr);
var manyItemArr = Array.from({ length: 1000 }, (_, i) => i);
var manyItemSet = new Set(manyItemArr);

Tests:

for of arr: few items
let result = 0; for (const item of fewItemArr) { result += item; }
for of set: few items
let result = 0; for (const item of fewItemSet) { result += item; }
native loop arr: few items
let result = 0; for (let i = fewItemArr.length; i--;) { result += fewItemArr[i]; }
native iter set: few items
let result = 0; let val = null; const iter = fewItemSet.values(); while (!(val = iter.next()).done) { result += val.value; }
for of arr: many items
let result = 0; for (const item of manyItemArr) { result += item; }
for of set: many items
let result = 0; for (const item of manyItemSet) { result += item; }
native loop arr: many items
let result = 0; for (let i = manyItemArr.length; i--;) { result += manyItemArr[i]; }
native iter set: many items
let result = 0; let val = null; const iter = manyItemSet.values(); while (!(val = iter.next()).done) { result += val.value; }

Run results for: Array iter vs set iter

Iterate over an array vs iterating over a set.

for of arr: few items

for of set: few items

native loop arr: few items

native iter set: few items

for of arr: many items

for of set: many items

native loop arr: many items

native iter set: many items