Run results for: JavaScript Fastest Array Copy

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.45 Safari/537.36

Browser: Chrome 96

Operating system: Windows

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
Array.concat	12028777.0 Ops/sec
Array.slice	13410901.0 Ops/sec
For loop	225684.2 Ops/sec
For loop with declared length	419293.9 Ops/sec
While loop	414411.2 Ops/sec
Spread operator	12194167.0 Ops/sec
Slice with begin argument	13313058.0 Ops/sec
Slice with begin and end argument	5343144.0 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