Run results for: new Intl.DateTimeFormat vs new Date().toLocaleDateString() vs re-using formatter

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36

Browser: Chrome 141

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 4 months ago

Test name	Executions per second
new Date()	1651587.2 Ops/sec
Intl.DateTimeFormat()	29953.3 Ops/sec
formatter	685493.9 Ops/sec

Script Preparation code:

var options = {
  year: 'numeric', month: 'numeric', day: 'numeric',
  hour: 'numeric', minute: 'numeric', second: 'numeric',
  hour12: false,
  fractionalSecondDigits: 3,
};
var formatter = new Intl.DateTimeFormat('en-US', options);

Tests:

new Date()
(new Date()).toISOString().trim().replace('T', ' ').replace('Z', '')
Intl.DateTimeFormat()
new Intl.DateTimeFormat('en-US', options).format(new Date())
formatter
formatter.format(new Date())

Run results for: new Intl.DateTimeFormat vs new Date().toLocaleDateString() vs re-using formatter

new Date()

Intl.DateTimeFormat()

formatter