Run results for: Concat vs push(...) vs spread

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser: Chrome 123

Operating system: Windows

Device Platform: Desktop

Date tested: 26 days ago

Test name	Executions per second
Concat	4360949.0 Ops/sec
Push spread	869511.6 Ops/sec
Spread 2	2877262.0 Ops/sec
Push	186723.6 Ops/sec

Script Preparation code:

var test1 = (new Array(50)).fill(0).map((d, i) => Math.random().toString());
var test2 = (new Array(50)).fill(0).map((d, i) => Math.random().toString());

Tests:

Concat
var both = test1.concat(test2); both[0] = both[50];
Push spread
var both = [].push(...test1, ...test2); both[0] = both[50];
Spread 2
var both = [...test1, ...test2]; both[0] = both[50];
Push
var len1 = test1.length; var len2 = test2.length; var both = new Array(len1 + len2); for (var i = 0; i < len1; ++i) both[i] = test1[i]; for (var i = 0; i < len2; ++i) both[i + len1] = test2[i]; both[0] = both[50];

Run results for: Concat vs push(...) vs spread

Comparing the various ways to append to an array

Concat

Push spread

Spread 2

Push