Run results for: Holey, Preallocated vs Packed, Pushed 3

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.212 Safari/537.36

Browser: Chrome 90

Operating system: Mac OS X 10.14.6

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
Create holey	1509110.4 Ops/sec
Create packed (push)	8045.4 Ops/sec
Create packed (assign)	8715.9 Ops/sec
Read holey	16943.9 Ops/sec
Read packed	16777.7 Ops/sec

Script Preparation code:

var holey = new Array(1000);
var packed = [];
var value = undefined;
var object = { value };
var store;
for(let i = 0; i < 1000; i++) packed.push(undefined);

Tests:

Create holey
holey = new Array(1000)
Create packed (push)
var packed = []; for(let i = 0; i < 1000; i++) packed.push(undefined);
Create packed (assign)
var packed = []; for(let i = 0; i < 1000; i++) packed[i] = undefined;
Read holey
store = holey[100]
Read packed
store = packed[100]
Read object
store = object.value;
Read value
store = value
Math
1+1
Create empty
store = []
Create empty, set length
store = []; store.length = 1000;
Create empty, set last
store = []; store[999] = undefined;
Create holey, fill
store = new Array(1000).fill(undefined)

Run results for: Holey, Preallocated vs Packed, Pushed 3

Create holey

Create packed (push)

Create packed (assign)

Read holey

Read packed

Read object

Read value

Math

Create empty

Create empty, set length

Create empty, set last

Create holey, fill