url-safe-base64/src/index.js

url safe base64 en- and decoding

/**
 * @module url-safe-base64
 * @license UNLICENSE
 * @example
 * import {
 *   encode, decode, trim,
 *   isBase64, isUrlSafeBase64
 * } from 'url-safe-base64'
 * const safe = encode('A/B+C==')
 * // > 'A-B_C..'
 * trim(safe)
 * // > 'A-B_C'
 * const base64 = decode(safe)
 * // > 'A/B+C=='
 * isBase64(base64)
 * // > true
 * isBase64(safe)
 * // > false
 * isUrlSafeBase64(base64)
 * // > false
 * isUrlSafeBase64(safe)
 * // > true
 */

const ENC = {
  '+': '-',
  '/': '_'
}
const DEC = {
  '-': '+',
  _: '/',
  '.': '='
}

/**
 * encode base64 string url safe
 * @param {String} base64 - base64 encoded string
 * @return {String} url-safe-base64 encoded
 */
export const encode = (base64) => {
  return base64.replace(/[+/]/g, (m) => ENC[m])
}

/**
 * decode url-safe-base64 string to base64
 * @param {String} safe - url-safe-base64 string
 * @return {String} base64 encoded
 */
export const decode = (safe) => {
  return safe.replace(/[-_.]/g, (m) => DEC[m])
}

/**
 * trim padding - `window.atob` might handle trimmed strings, e.g. in Chrome@57, Firefox@52
 * @param {String} string - base64 or url-safe-base64 string
 * @return {String} string with padding chars removed
 */
export const trim = (string) => {
  return string.replace(/[.=]{1,2}$/, '')
}

/**
 * checks if `string` is base64 encoded
 * @param {String} string
 * @return {Boolean} true if base64 encoded
 */
export const isBase64 = (string) => /^[A-Za-z0-9+/]*[=]{0,2}$/.test(string)

/**
 * checks if `string` is url-safe-base64 encoded
 * @param {String} string
 * @return {Boolean} true if url-safe-base64 encoded
 */
export const isUrlSafeBase64 = (string) => /^[A-Za-z0-9_-]*[.=]{0,2}$/.test(string)