lex62ts

Fast, lexicographic base62 encode and decode

Installation

# using npm
npm i --save lex62ts
# or using yarn
yarn add -D lex62ts

Design notes

• ideas from http://www.zanopha.com/docs/elen.pdf
• lexigraphical order: A < Z < a < z < 0 < 9
• ensures lexicographical order by appending an alphabetic prefix (based on number of digits).
• decode will only work with base64 numbers that have an expected prefix (alphabetic prefix appended to ensure lexigraphic order).
• encode should work with any safe positive integer (and zero) as long as it is not very large ~> 1e90 (see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger).

Typescript

This library is written in and therefore fully supports Typescript. The commonjs module is compiled for and tested with Node16.

Usage

encode

import { encode } from 'lex62ts'

encode(0) // 'A0'
encode(1) // 'A1'
encode(9) // 'A9'
encode(10) // 'AA'
encode(35) // 'AZ'
encode(36) // 'Aa'
encode(61) // 'Az'
encode(62) // 'B10'
encode(123) // 'B1z'
encode(3843) // 'Bzz'
encode(3844) // 'C100'
encode(238327) // 'Czzz'

// errors
encode('yo')
// throws [Error: 'encode: invalid number (not an integer)']
encode(-10)
// throws [Error: 'encode: unsupported number (must be a positive integer or zero)']
encode(1e90)
// throws [Error: 'encode: unsupported number (too large)']

decode

• decode only works w/ base62 numbers which follow the format outputted by encode.

import { decode } from 'lex62ts'

decode('A0') // 0
decode('A1') // 1
decode('A9') // 9
decode('AA') // 10
decode('AZ') // 35
decode('Aa') // 36
decode('Az') // 61
decode('B10') // 62
decode('B1z') // 123
decode('Bzz') // 3843
decode('C100') // 3844
decode('Czzz') // 238327

// errors
decode('A*')
// throws [Error: 'decode: invalid string ("A*" not base62)']
decode('B0')
// throws [Error: 'decode: unsupported number (unexpected prefix)']
decode('B00')
// throws [Error: 'decode: unsupported number (unexpected zero)']
decode('zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz')
// throws [Error: 'decode: unsupported number (too large)']

License

MIT