Run results for: Array concat vs spread vs push spread, loop, apply, assign

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_3 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) CriOS/100.0.4896.77 Mobile/15E148 Safari/604.1

Browser: Chrome Mobile iOS 100

Operating system: iOS 15.3

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
Array.prototype.concat	977001.1 Ops/sec
spread operator	919354.9 Ops/sec
Push Spread	630730.6 Ops/sec
Push Apply	742602.8 Ops/sec
Push Loop	823713.5 Ops/sec
Assign length loop	826989.2 Ops/sec
minified assign loop	859359.8 Ops/sec

Script Preparation code:

var subarrs = [
 [ "hello", true, 7 ],
 [ "yes", "no", "maybe", false, 27 ],
 [ 16, "I", "wonder", "what", "will", "be", "fastest"]
];

Tests:

Array.prototype.concat
var other = [ 1, 2, 3 ] for (var len = subarrs.length, i = 0; i < len; i++){ other = other.concat(subarrs[i]); }
spread operator
var other = [ 1, 2, 3 ] for (var len = subarrs.length, i = 0; i < len; i++){ other = [ ...other, ...subarrs[i] ] }
Push Spread
var other = [ 1, 2, 3 ] for (var len = subarrs.length, i = 0; i < len; i++){ other.push(...subarrs[i]); }
Push Apply
var other = [ 1, 2, 3 ] for (var len = subarrs.length, i = 0; i < len; i++){ other.push.apply(other, subarrs[i]); }
Push Loop
var other = [ 1, 2, 3 ] for (var len = subarrs.length, i = 0; i < len; i++){ for (var jarr = subarrs[i], jen = jarr.length, j = 0; j < jen; j++){ other.push(jarr[j]); } }
Assign length loop
var other = [1, 2, 3]; for (var i = 0, j, m, a, n = subarrs.length; i < n; ++i) for (j = 0, a = subarrs[i], m = a.length; j < m; ++j) other[other.length] = a[j];
minified assign loop
for(var r,s,a,e=[1,2,3],g=0,h=subarrs.length;g<h;++g)for(r=0,s=(a=subarrs[g]).length;r<s;++r)e[e.length]=a[r];

Run results for: Array concat vs spread vs push spread, loop, apply, assign

Compare the new ES6 spread operator with the traditional concat() method and push

Array.prototype.concat

spread operator

Push Spread

Push Apply

Push Loop

Assign length loop

minified assign loop