Run results for: Initializing array with n undefined items

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_0_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0.1 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 18

Operating system: iOS 18.0.1

Device Platform: Mobile

Date tested: 29 days ago

Test name	Executions per second
[...Array(n).keys()].map(k => undefined)	210.9 Ops/sec
Array.apply(null, { length: 4 })	0.0 Ops/sec
Array.from	220.6 Ops/sec
Array(n).fill(undefined)	18228.0 Ops/sec
for loop push	151.9 Ops/sec

Script Preparation code:

var n = 100000; // 100k

Tests:

[...Array(n).keys()].map(k => undefined)
[...Array(n).keys()].map(k => undefined);
Array.apply(null, { length: 4 })
Array.apply(null, { length: n });
Array.from
Array.from({ length: n }, () => undefined);
Array(n).fill(undefined)
Array(n).fill(undefined)
for loop push
const arr = []; for (let i = 0; i < n; i++) { arr.push(undefined); }

Run results for: Initializing array with n undefined items

worth to note that the maximum callstack size is exceeded for the first test case (spread operator) with n = 1 million

[...Array(n).keys()].map(k => undefined)

Array.apply(null, { length: 4 })

Array.from

Array(n).fill(undefined)

for loop push