Package Exports

lex62ts
lex62ts/lib/index.js

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Readme

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