Based on is-canonical-base64 but modified to generate regular expressions for url-safe base64, as described in ssb-uri spec :
URI-safe Base64 is equivalent to Base64 where + characters are replaced with -, and / characters are replaced with _.
const Butt64 = require('butt64')
const regex = new Butt64('ssb:feed/classic/, null, 32)
regex.test('ssb:feed/classic/-oaWWDs8g73EZFUMfW37R_ULtFEjwKN_DczvdYihjbU=')
// => true
All arguments are optional
prefix
String or Pattern to require at the beginning of stringsuffix
String or Pattern pattern to require at the end of stringlength
Integer the length of the data in bytes you're expected to be encoded
Converts a buffer ing a base64 encoded string.
Converts a butt64 encoded string into a buffer.
MIT