Run results for: Array initialization: preallocate vs push vs preallocate & fill

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/134.0.6998.99 Mobile/15E148 Safari/604.1

Browser: Chrome Mobile iOS 134

Operating system: iOS 18.3.2

Device Platform: Mobile

Date tested: one year ago

Preallocate

153K/s

Preallocate & fill

92K/s

Push

67K/s

Index

64K/s

View exact numbers

Test name	Executions per second
✓ Preallocate	152,548 Ops/sec
Preallocate & fill	92,215 Ops/sec
Push	66,753 Ops/sec
Index	64,239 Ops/sec

Tests:

Preallocate
var N = 10000; var result = new Array(N); for (var i = 0; i < N; i++) { result[i] = i * 2; }
Preallocate & fill
var N = 10000; var result = new Array(N).fill(0); for (var i = 0; i < N; i++) { result[i] = i * 2; }
Push
var N = 10000; var result = []; for (var i = 0; i < N; i++) { result.push(i * 2); }
Index
var N = 10000; var result = []; for (var i = 0; i < N; i++) { result[i] = i * 2; }