es-arraybuffer-base64/aos/helpers/alphabetFromIdentifier.js

An ES-spec-compliant shim/polyfill/replacement for ArrayBuffer base64 methods that works as far down as ES3

'use strict';

var base64Characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
var base64UrlCharacters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';

var $TypeError = require('es-errors/type');

module.exports = function alphabetFromIdentifier(alphabet) {
	if (alphabet === 'base64') {
		return base64Characters;
	}

	if (alphabet === 'base64url') {
		return base64UrlCharacters;
	}

	throw new $TypeError('expected alphabet to be either "base64" or "base64url"');
};