Run results for: JavaScript Fastest Array Copy

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:150.0) Gecko/20100101 Firefox/150.0

Browser: Firefox 150

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: 5 days ago

Test name	Executions per second
Array.concat	24338184.0 Ops/sec
Array.slice	32993010.0 Ops/sec
For loop	14429202.0 Ops/sec
For loop with declared length	14727930.0 Ops/sec
While loop	15078051.0 Ops/sec
Spread operator	6426543.0 Ops/sec
Slice with begin argument	32890174.0 Ops/sec
Slice with begin and end argument	32798278.0 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