Run results for: string.split vs string.substring vs toLocaleDateString("pt-PT") vs Intl.DateTimeateTimeFormat

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:136.0) Gecko/20100101 Firefox/136.0

Browser: Firefox 136

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
split	9663759.0 Ops/sec
Date toLocaleString without date being cached	5636.4 Ops/sec
slice	676450816.0 Ops/sec
substring	733038336.0 Ops/sec
Intl no format cache no date cache	6414.0 Ops/sec
Intl no format cache with date cache	6546.7 Ops/sec
Intl with format cache no date cache	322170.4 Ops/sec
Intl with format cache with date cache	394237.5 Ops/sec
Date toLocaleString with date being cached	5870.1 Ops/sec

Script Preparation code:

var dateStr = "2021-08-10";
var dateDate = new Date(dateStr);
var formatter = new Intl.DateTimeFormat("pt-PT");

Tests:

split
const [yyyy, mm, dd] = dateStr.split("/"); const result =`${dd}/${mm}/${yyyy}`;
Date toLocaleString without date being cached
const result = new Date(dateStr).toLocaleString("pt-PT");
slice
const day = dateStr.slice(8, 10); const month = dateStr.slice(5, 7); const year = dateStr.slice(0, 4); const result = `${day}/${month}/${year}`
substring
const day = dateStr.substring(8, 10); const month = dateStr.substring(5, 7); const year = dateStr.substring(0, 4); const result = `${day}/${month}/${year}`
Intl no format cache no date cache
const result = new Intl.DateTimeFormat("pt-PT").format(new Date(dateStr));
Intl no format cache with date cache
const result = new Intl.DateTimeFormat("pt-PT").format(dateDate);
Intl with format cache no date cache
const result = formatter.format(new Date(dateStr));
Intl with format cache with date cache
const result = formatter.format(dateDate);
Date toLocaleString with date being cached
const result = dateDate.toLocaleString("pt-PT");