Benchmark: Array.prototype.concat vs splice vs loop for joining lots of arrays

Tests:

immutable with concat
var a = [] var b = [ "hello", "jello" ] for (var i = 0; i < 1000; i++) { a = a.concat(b) }
mutation with splice + spread
var a = [] var b = [ "hello", "jello" ] for (var i = 0; i < 1000; i++) { a.splice(a.length, 0, ...b) }
mutation with splice into preallocated array
var a = new Array(2000) var b = [ "hello", "jello" ] for (var i = 0; i < 1000; i++) { a.splice(i * b.length, b.length, ...b) }
mutation with loop-assign
var a = new Array(2000) var b = [ "hello", "jello" ] for (var i = 0; i < 1000; i++) { for (var j = 0; j < b.length; j++) { a[i+j] = b[j] } }

Rendered benchmark preparation results:

Previous results

Test case name	Result
immutable with concat
mutation with splice + spread
mutation with splice into preallocated array
mutation with loop-assign

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Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Android 9; Tablet; rv:66.0) Gecko/66.0 Firefox/66.0

Browser/OS: Firefox 66 on Android

Test name	Executions per second
immutable with concat	23.4 Ops/sec
mutation with splice + spread	951.9 Ops/sec
mutation with splice into preallocated array	1024.8 Ops/sec
mutation with loop-assign	24848.8 Ops/sec

Array.prototype.concat vs splice vs loop for joining lots of arrays (version: 0)