Run results for: JavaScript Fastest Array Copy

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:141.0) Gecko/20100101 Firefox/141.0

Browser: Firefox 141

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Slice with begin argument

13.4M/s

Slice with begin and end argument

13.3M/s

Array.slice

13.3M/s

Array.concat

11.6M/s

For loop

5.7M/s

For loop with declared length

5.7M/s

While loop

5.5M/s

Spread operator

2.6M/s

View exact numbers

Test name	Executions per second
✓ Slice with begin argument	13,425,085 Ops/sec
Slice with begin and end argument	13,346,659 Ops/sec
Array.slice	13,319,632 Ops/sec
Array.concat	11,608,431 Ops/sec
For loop	5,713,355 Ops/sec
For loop with declared length	5,695,331 Ops/sec
While loop	5,470,597 Ops/sec
Spread operator	2,594,419 Ops/sec

Script Preparation code:

var arrayToCopy = [ "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello", "hello" ];

Tests:

Array.concat
var shallowCopy = arrayToCopy.concat();
Array.slice
var shallowCopy = arrayToCopy.slice();
For loop
var shallowCopy = []; for (let i = 0; i < arrayToCopy.length; ++i) { shallowCopy.push(arrayToCopy[i]); }
For loop with declared length
var shallowCopy = []; var arrayLength = arrayToCopy.length; for (let i = 0; i < arrayLength; ++i) { shallowCopy.push(arrayToCopy[i]); }
While loop
var shallowCopy = []; let i = arrayToCopy.length - 1; while (i--) { shallowCopy.push(arrayToCopy[i]); }
Spread operator
var shallowCopy = [...arrayToCopy];
Slice with begin argument
var shallowCopy = arrayToCopy.slice(0);
Slice with begin and end argument
var shallowCopy = arrayToCopy.slice(0, arrayToCopy.length);