Run results for: Array.prototype.concat vs splice for joining lots of arrays

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.75 Safari/537.36

Browser: Chrome 73

Operating system: Mac OS X 10.14.0

Device Platform: Desktop

Date tested: 5 years ago

Test name	Executions per second
immutable with concat	474.6 Ops/sec
direct mutation with splice + spread	4071.4 Ops/sec

Tests:

immutable with concat
var a = [] var b = [ "hello", "jello" ] for (var i = 0; i < 1000; i++) { a = a.concat(b) }
direct mutation with splice + spread
var a = [] var b = [ "hello", "jello" ] for (var i = 0; i < 1000; i++) { a.splice(0, a.length, ...b) }