Run results for: cached Number.toLocaleString vs Intl.NumberFormat

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:133.0) Gecko/20100101 Firefox/133.0

Browser: Firefox 133

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
Number.toLocaleString	15425.8 Ops/sec
Intl.NumberFormat	647574.1 Ops/sec

HTML Preparation code:

<script>
    function toLocaleString(number = NaN, decimals) {
        return number.toLocaleString('en-US', {
            maximumFractionDigits: decimals,
            minimumFractionDigits: decimals,
        });
    };

    const numberFormatter = new Intl.NumberFormat('en-US');
    const formatCache = new Map();

    function formatNumber(number = NaN, decimals) {
        // Handle NaN early to avoid unnecessary processing
        if (isNaN(number)) {
            return 'NaN';
        }

        // Use cached formatter if decimals are undefined
        if (decimals === undefined) {
            return numberFormatter.format(number);
        }

        // Cache and reuse formatters for specific decimal places
        let formatter = formatCache.get(decimals);
        if (!formatter) {
            formatter = new Intl.NumberFormat('en-US', {
                maximumFractionDigits: decimals,
                minimumFractionDigits: decimals,
            });
            formatCache.set(decimals, formatter);
        }

        return formatter.format(number);
    };
</script>

Script Preparation code:

const formatter = new Intl.NumberFormat(undefined, {
    style: 'currency',
    currency: 'RUB',
});

Tests:

Number.toLocaleString
toLocaleString(1000000, 1); toLocaleString(1000000, 2); toLocaleString(1000000, 10); toLocaleString(1000000, 8); toLocaleString(1000000, 12);
Intl.NumberFormat
formatNumber(1000000, 1); formatNumber(1000000, 2); formatNumber(1000000, 10); formatNumber(1000000, 8); formatNumber(1000000, 12);