Run results for: Intl.NumberFormat vs toLocaleString vs Custom Formatter vs Pre-created Intl formatter

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Browser: Chrome 108

Operating system: Windows

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
Intl.NumberFormat	21490.0 Ops/sec
toLocalString	23346.4 Ops/sec
Custom Formatter	546538.0 Ops/sec
Pre-created Intl formatter	1024257.2 Ops/sec

Script Preparation code:

function formatUSD(a) {
	const [str, fraction] = String(a).split('.');
	return '$' + str.split('').reverse().join('').match(/\d{1,3}/g).join().split('').reverse().join('') + '.' + fraction;
}

var formatIntlUSD = new Intl.NumberFormat("en-US", { style: 'currency', currency: 'USD' });

Tests:

Intl.NumberFormat
var a = new Intl.NumberFormat("en-US", { style: 'currency', currency: 'USD' }).format(10000.56);
toLocalString
var a = (10000.56).toLocaleString("en-US", { style: 'currency', currency: 'USD' });
Custom Formatter
var a = formatUSD(10000.56);
Pre-created Intl formatter
var a = formatIntlUSD.format(10000.56);

Run results for: Intl.NumberFormat vs toLocaleString vs Custom Formatter vs Pre-created Intl formatter

Intl.NumberFormat

toLocalString

Custom Formatter

Pre-created Intl formatter