numradix

Number base conversion toolkit — bases 2–36, BigInt precision, custom alphabets. Zero dependencies. TypeScript-first.

Features

• Convert between any bases from 2 to 36 — binary, octal, decimal, hex, base36 and everything in between
• No precision loss — uses BigInt internally, handles arbitrarily large numbers
• Convenient shorthands: toBin, toOct, toDec, toHex
• Custom alphabets — Base58, Base62, Base64URL or your own
• Output formatting — prefix (0x, 0b), digit grouping, padding, uppercase
• Written in TypeScript — ships with full type declarations
• Zero runtime dependencies
• Works in Node.js, Deno, Bun, and modern browsers
• ESM + CommonJS dual build

Install

npm install numradix
# or
pnpm add numradix
# or
yarn add numradix

Usage

import { convert, toBin, toHex, format, isValid } from 'numradix'

// Core conversion
convert('ff', 16, 10)        // '255'
convert('255', 10, 2)        // '11111111'
convert('777', 8, 16)        // '1ff'

// Shorthands
toBin(255)                   // '11111111'
toBin('ff', 16)              // '11111111'
toHex(255)                   // 'ff'
toHex('11111111', 2)         // 'ff'

// Validation
isValid('ff', 16)            // true
isValid('fg', 16)            // false

// Formatting
format(toHex(255), { prefix: '0x', uppercase: true, padStart: 4 })
// '0x00FF'

format(toBin(255), { prefix: '0b', groupSize: 4, separator: '_' })
// '0b1111_1111'

CommonJS (require) is also supported:

const { convert, toHex } = require('numradix')

convert('ff', 16, 10)  // '255'
toHex(255)             // 'ff'

API

convert(value, fromBase, toBase)

Convert a number from one base to another. Accepts string, number, or bigint. For number and bigint inputs, fromBase is ignored — the value is used as-is.

convert(value: string | number | bigint, fromBase: number, toBase: number): string

convert('ff', 16, 10)          // '255'
convert('255', 10, 2)          // '11111111'
convert(255, 10, 16)           // 'ff'
convert(255n, 10, 2)           // '11111111'

// No precision loss on large numbers
convert('9007199254740993', 10, 16)   // '20000000000001'

Throws RangeError if base is not an integer between 2 and 36. Throws Error if the string contains a character invalid for the given base.

Shorthands

Function	Converts to	Default fromBase
toBin(value, fromBase?)	Binary (base 2)	10
toOct(value, fromBase?)	Octal (base 8)	10
toDec(value, fromBase)	Decimal (base 10)	—
toHex(value, fromBase?)	Hex (base 16)	10

toBin(255)            // '11111111'
toBin('ff', 16)       // '11111111'
toOct(255)            // '377'
toDec('ff', 16)       // '255'
toHex(255)            // 'ff'

isValid(value, base)

Check whether a string is a valid number in the given base. Trims leading/trailing whitespace before checking.

isValid('ff', 16)      // true
isValid('fg', 16)      // false
isValid(' 1010 ', 2)   // true
isValid('', 10)        // false

parseBigInt(value, base) / stringifyBigInt(value, base)

Convert between string representations and native bigint.

parseBigInt('ff', 16)                    // 255n
parseBigInt('ffffffffffffffff', 16)      // 18446744073709551615n

stringifyBigInt(255n, 16)               // 'ff'
stringifyBigInt(255n, 2)                // '11111111'

encodeCustom(value, alphabet) / decodeCustom(value, alphabet)

Encode and decode integers using a custom character alphabet. Use ALPHABETS for common presets.

When value is a string, it must be a decimal integer string. For other bases, parse first: encodeCustom(parseBigInt('ff', 16), ALPHABETS.BASE62)

import { encodeCustom, decodeCustom, ALPHABETS } from 'numradix'

encodeCustom(1337n, ALPHABETS.BASE62)           // 'LZ'
decodeCustom('LZ', ALPHABETS.BASE62)            // 1337n

encodeCustom(255n, '0123456789ABCDEF')          // 'FF'
decodeCustom('FF', '0123456789ABCDEF')          // 255n

ALPHABETS

Key	Description	Use case
ALPHABETS.BASE62	0-9 a-z A-Z (62 chars)	Short IDs, URL tokens
ALPHABETS.BASE58	Base62 without 0 O I l (58 chars)	Bitcoin addresses, QR codes
ALPHABETS.BASE64URL	A-Z a-z 0-9 - _ (64 chars)	URL-safe encoding, JWT

format(value, options?)

Format a converted number string — add prefix, group digits, pad, or change case.

format('11111111', { prefix: '0b', groupSize: 4, separator: '_' })
// '0b1111_1111'

format('ff', { prefix: '0x', uppercase: true, padStart: 4 })
// '0x00FF'

format('deadbeef', { uppercase: true, groupSize: 4, separator: ' ' })
// 'DEAD BEEF'

Option	Type	Default	Description
prefix	string	''	String to prepend (e.g. '0x', '0b')
groupSize	number	—	Split digits into groups of N (right-to-left)
separator	string	' '	Character between groups
uppercase	boolean	false	Convert letters to uppercase
padStart	number	—	Minimum digit count, padded with '0'

BigInt and precision

JavaScript number can only represent integers exactly up to 2^53 − 1. This library uses BigInt for all internal computations, so there is no precision loss regardless of input size.

// Standard JS loses precision here:
Number('9007199254740993') === Number('9007199254740992')  // true — wrong!

// numradix is accurate:
convert('9007199254740993', 10, 16)  // '20000000000001'
convert('20000000000001', 16, 10)    // '9007199254740993' ✓

Note: if you pass a number (not a string) beyond Number.MAX_SAFE_INTEGER, precision is already lost before the library sees it. Use a string or bigint for large values.

Development

git clone https://github.com/MaxGrushevsky/numradix.git
cd numradix
npm install

npm run build         # compile to dist/
npm test              # run tests once
npm run test:watch    # run tests in watch mode
npm run typecheck     # TypeScript type-check only

License

MIT