Package Exports

lex62

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Readme

lex62

Fast, lexicographic base62 encode and decode

Installation

npm i --save lex62

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 positive integer (and zero) as long as it is not very large ~> 1e90.

Usage

encode

var lex62 = require('lex62')

lex62.encode(0) // 'A0'
lex62.encode(1) // 'A1'
lex62.encode(9) // 'A9'
lex62.encode(10) // 'AA'
lex62.encode(35) // 'AZ'
lex62.encode(36) // 'Aa'
lex62.encode(61) // 'Az'
lex62.encode(62) // 'B10'
lex62.encode(123) // 'B1z'
lex62.encode(3843) // 'Bzz'
lex62.encode(3844) // 'C100'
lex62.encode(238327) // 'Czzz'

// errors
lex62.encode('yo')
// throws [AssertionError: 'encode: invalid base10 (not a number)']
lex62.encode(-10)
// throws [AssertionError: 'encode: number not supported (must be a positive integer or zero)']
lex62.encode(1e90)
// throws [AssertionError: 'encode: number not supported (too large)']

decode

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

var lex62 = require('lex62')

lex62.encode('A0') // 0
lex62.encode('A1') // 1
lex62.encode('A9') // 9
lex62.encode('AA') // 10
lex62.encode('AZ') // 35
lex62.encode('Aa') // 36
lex62.encode('Az') // 61
lex62.encode('B10') // 62
lex62.encode('B1z') // 123
lex62.encode('Bzz') // 3843
lex62.encode('C100') // 3844
lex62.encode('Czzz') // 238327

// errors
lex62.encode('A*')
// throws [AssertionError: 'decode: invalid base62 ("A*" not base62)']
lex62.encode('B0')
// throws [AssertionError: 'decode: number not supported (unexpected prefix)']
lex62.encode('B00')
// throws [AssertionError: 'decode: number not supported (unexpected zero)']
lex62.encode('zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz')
// throws [AssertionError: 'decode: number not supported (too large)']

License

MIT