Run results for: JavaScript Fastest Array Copy

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:94.0) Gecko/20100101 Firefox/94.0

Browser: Firefox 94

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
Array.concat	2741421.8 Ops/sec
Array.slice	13558748.0 Ops/sec
For loop	2436839.0 Ops/sec
For loop with declared length	2893529.8 Ops/sec
While loop	2739523.2 Ops/sec
Spread operator	2172001.0 Ops/sec
Slice with begin argument	13160020.0 Ops/sec
Slice with begin and end argument	13894270.0 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