numeral-2-0-6 - SKILL.md Agent Skill

name: numeral-2-0-6 description: A JavaScript library for formatting and manipulating numbers. Use when formatting currency, percentages, bytes, time durations, ordinals, exponential notation, or abbreviations in browser or Node.js applications.

Numeral.js 2.0.6

Overview

Numeral.js is a lightweight JavaScript library (~6 KB minified) for formatting and manipulating numbers. It provides a fluent API for converting raw numeric values into human-readable strings — currency, percentages, file sizes, ordinals, time durations, exponential notation, and abbreviated forms (k, m, b, t).

It supports 34 built-in locales with localized delimiters, abbreviations, ordinal rules, and currency symbols. Locales are registered via numeral.register() and switched at runtime with numeral.locale().

The library handles floating-point precision issues in arithmetic operations through an internal correction factor, making it suitable for financial calculations where 0.1 + 0.2 !== 0.3 matters.

When to Use

Formatting numbers as currency ($1,234.56, €1.234,56)
Displaying percentages (45.5%)
Showing file sizes in human-readable form (2.35 MB, 1.0 GiB)
Abbreviating large numbers (2.5k, 3.1m)
Formatting ordinal numbers (1st, 2nd, 3rd, 4th)
Converting seconds to time strings (1:05:30)
Exponential notation formatting (1.23e+5)
Parsing formatted number strings back to numeric values (auto-unformat on construction)
Performing arithmetic with reduced floating-point drift (add, subtract, multiply, divide)

Installation

npm install numeral

<!-- CDN -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/numeral.js/2.0.6/numeral.min.js"></script>

CommonJS / ES module usage:

const numeral = require('numeral');
// or
import numeral from 'numeral';

Core API

Construction

Create a numeral instance from a number, string, or null:

numeral(1234.56)        // → Numeral { _value: 1234.56 }
numeral('1,234.56')     // → Numeral { _value: 1234.56 } (auto-unformat)
numeral(null)           // → Numeral { _value: null }
numeral(NaN)            // → Numeral { _value: null }
numeral(0)              // → Numeral { _value: 0 }

String inputs are automatically parsed using the current locale's delimiters and abbreviations. The old unformat() method was removed in v2.0 — unformatting now happens at construction time.

Instance Methods

format([string], [roundingFunction]) — Format the value as a string:

numeral(1234567.89).format('0,0')       // "1,234,568"
numeral(1234567.89).format('0,0.00')    // "1,234,567.89"
numeral(1234567.89).format('0.0a')      // "1.2m"
numeral(0.95).format('0,0%')            // "95%"

value() — Get the underlying numeric value. input() — Get the original input passed to the constructor. set(value) — Change the underlying value. add(value) / subtract(value) / multiply(value) / divide(value) — Arithmetic with floating-point correction. difference(value) — Absolute difference. clone() — Create a new numeral instance with the same value.

Global Options

numeral.locale('de');                    // switch to German
numeral.defaultFormat('$0,0.00');        // default for .format() with no arg
numeral.zeroFormat('—');                 // custom string for zero values
numeral.nullFormat('N/A');               // custom string for null values
numeral.reset();                         // reset all options to defaults
numeral.options.scalePercentBy100 = false;  // disable percent scaling

Registration and Validation

// Register a custom locale
numeral.register('locale', 'custom', {
    delimiters: { thousands: "'", decimal: '.' },
    abbreviations: { thousand: 'k', million: 'm', billion: 'b', trillion: 't' },
    ordinal: function(number) { return 'th'; },
    currency: { symbol: '¤' }
});

// Validate a string as a properly formatted number
numeral.validate('1,234.56')              // true
numeral.validate('1,23,456')              // false

Built-in Locales

Numeral.js ships with 34 locales: bg, chs, cs, da-dk, de, de-ch, en (default), en-au, en-gb, en-za, es-es, fr-fr, it-it, ja, ko, lt, lv, nb-no, nl-nl, pl, pt-br, pt-pt, ro, ru, sk, sl, sr, sv, tr, uk, vi, and others.

Migration Notes (v1.x to v2.0)

unformat() removed — Parsing happens at construction: numeral('1,234')
language renamed to locale — Use numeral.locale() and numeral.localeData()
Formats are separate files — Loaded via numeral.register('format', name, {})
Locales standardized — All lowercase keys
Bytes format changed — b is base 1000 (decimal), ib is base 1024 (binary/IEC)
NaN treated as null — No longer throws an error

Advanced Topics

API Reference: Instance methods, format strings, rounding — API & Format Strings Usage Examples: Financial dashboards, file sizes, i18n, arithmetic — Usage Examples