Run results for: for key in object iteration vs for of array iteration

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36

Browser: Chrome 136

Operating system: Linux

Device Platform: Desktop

Date tested: 11 months ago

Test name	Executions per second
Obj key for in iteration	13380.0 Ops/sec
Array key for of iteration	89415.0 Ops/sec
Obj key precreate keys for of iteration	15638.0 Ops/sec
Array tuple for of iteration	576242.8 Ops/sec
Precomputed obj keys iterative obj key access	89040.1 Ops/sec
Array tuple stack pop	320708.2 Ops/sec
Array tuple for index iteration	267523.6 Ops/sec

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

const obj = {};
const array = [];
const arrayTuples = [];

let expectedSum = 0;
for (let i = 0; i < 1000; i++){
	const letterNum1 = i % 27;
  	const letterNum2 = i % 5;
  	const letterNum3 = i % 13;
  	const key = String.fromCharCode(letterNum1 + 65, letterNum2 + 65, letterNum3 + 65)
    
    obj[key] = i;
    array.push(key);
	arrayTuples.push([key, i])
    
    expectedSum += i;
}
const preComputedKeys = Object.keys(obj);

Tests:

Obj key for in iteration
const arrayPop = [].concat(arrayTuples); let number = 0; for (const key in obj){ number += obj[key]; } return number === expectedSum
Array key for of iteration
const arrayPop = [].concat(arrayTuples); let number = 0; for (const key of array){ number += obj[key]; } return number === expectedSum
Obj key precreate keys for of iteration
const arrayPop = [].concat(arrayTuples); const keys = Object.keys(obj); let number = 0; for (const key of keys){ number += obj[key]; } return number === expectedSum
Array tuple for of iteration
const arrayPop = [].concat(arrayTuples); let number = 0; for (const tuple of arrayTuples){ number += tuple[1]; } return number === expectedSum
Precomputed obj keys iterative obj key access
const arrayPop = [].concat(arrayTuples); let number = 0; for (const key of preComputedKeys){ number += obj[key]; } return number === expectedSum
Array tuple stack pop
// I think calling pop removes items for following test runs // --> appears too fast without cloning the array const arrayPop = [].concat(arrayTuples); let number = 0; while (arrayPop.length > 0){ const item = arrayPop.pop(); number += item[1]; } return number === expectedSum
Array tuple for index iteration
const arrayPop = [].concat(arrayTuples); let number = 0; for (let i = 0; i < arrayTuples.length; i++){ number += arrayTuples[i][1]; } return number === expectedSum

Run results for: for key in object iteration vs for of array iteration

Obj key for in iteration

Array key for of iteration

Obj key precreate keys for of iteration

Array tuple for of iteration

Precomputed obj keys iterative obj key access

Array tuple stack pop

Array tuple for index iteration