Run results for: JavaScript Fastest Array Copy

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36

Browser: Chrome 103

Operating system: Mac OS X 10.11.6

Device Platform: Desktop

Date tested: 8 months ago

Array.slice

110.3M/s

Slice with begin argument

108.5M/s

Array.concat

68.7M/s

Spread operator

53.0M/s

Slice with begin and end argument

23.2M/s

For loop with declared length

2.0M/s

While loop

2.0M/s

For loop

1.9M/s

View exact numbers

Test name	Executions per second
✓ Array.slice	110,291,744 Ops/sec
Slice with begin argument	108,531,112 Ops/sec
Array.concat	68,672,136 Ops/sec
Spread operator	53,018,892 Ops/sec
Slice with begin and end argument	23,155,362 Ops/sec
For loop with declared length	2,039,135 Ops/sec
While loop	2,033,041 Ops/sec
For loop	1,909,685 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);