Run results for: JavaScript Fastest Array Copy

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:140.0) Gecko/20100101 Firefox/140.0

Browser: Firefox 140

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: 2 months ago

Test name	Executions per second
Array.concat	21894998.0 Ops/sec
Array.slice	28752156.0 Ops/sec
For loop	13548329.0 Ops/sec
For loop with declared length	14081447.0 Ops/sec
While loop	14136434.0 Ops/sec
Spread operator	5825780.0 Ops/sec
Slice with begin argument	29045520.0 Ops/sec
Slice with begin and end argument	29084336.0 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);

Run results for: JavaScript Fastest Array Copy

Testing the results for the fastest approach of shallow copying an array in JavaScript (concat, slice, for loop, while loop, spread operator).

Array.concat

Array.slice

For loop

For loop with declared length

While loop

Spread operator

Slice with begin argument

Slice with begin and end argument