Run results for: for-of-vs-map-bad

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 17_5_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.5 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 17

Operating system: iOS 17.5.1

Device Platform: Mobile

Date tested: 11 months ago

for of

93K/s

bad map

92K/s

map

61K/s

View exact numbers

Test name	Executions per second
✓ for of	92,674 Ops/sec
bad map	92,321 Ops/sec
map	61,355 Ops/sec

Script Preparation code:

var arr = [];
for (var i = 0; i < 1000; i++) {
    arr[i] = {
        name: `${i}`,
        value: i
    };
}

function someFn(i) {
    const x24 = i.value * 3 * 8;
    i.value = x24;
    i.name = `${x24}`;
    return i;
}

Tests:

for of
const x = Array(arr.length) for (var y of arr) { x.push(someFn(y)); }
map
const x = arr.map(item => someFn(item))
bad map
const x = arr.map((i) => { const x24 = i.value * 3 * 8; i.value = x24; i.name = `${x24}`; return i; })