Math and Intl.NumberFormat

                Math.round(n) / Math.max(...ns) / new Intl.NumberFormat(locale, options).format(n)
              

Purpose

Math provides standard numeric operations beyond the basic arithmetic operators. Intl.NumberFormat formats a number for a human reader — currency, percentages, grouping separators — correctly for a given locale, instead of hand-building the string.

Common Math members

Math.round(4.6); // 5
Math.floor(4.6); // 4
Math.ceil(4.1); // 5
Math.abs(-7); // 7
Math.max(3, 7, 2); // 7
Math.min(3, 7, 2); // 2
Math.random(); // a float in [0, 1)

Intl.NumberFormat

const usd = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' });
usd.format(1234.5); // "$1,234.50"

new Intl.NumberFormat('en-US', { style: 'percent' }).format(0.42); // "42%"
new Intl.NumberFormat('de-DE').format(1234.5); // "1.234,5" — different grouping/decimal marks

Behavior notes

• Math.random() never returns exactly 1, only values from 0 up to (not including) 1. A random integer in a range is built from it: Math.floor(Math.random() * (max - min + 1)) + min.
• Intl.NumberFormat is locale-aware: grouping separators, decimal marks, and currency symbol placement all follow the given locale’s conventions, not a fixed format.
• Creating an Intl.NumberFormat instance has a small cost — reuse one formatter instance for many .format() calls rather than constructing a new one every time in a loop.

Common mistakes

• Hand-building a formatted price string ('$' + n.toFixed(2)) instead of using Intl.NumberFormat — breaks down for other currencies, locales, and large numbers needing grouping separators.
• Assuming Math.round(-0.5) rounds toward negative infinity — it rounds half-values up (toward positive infinity), so Math.round(-0.5) is -0, not -1.

Runtime notes

Math is core ECMAScript; Intl is part of the ECMAScript Internationalization API, supported in every current browser and Node version, though available locales can vary slightly by platform.