base64.js

Yet another Base64 transcoder

HEADS UP: ES2015 support required since version 3

Version 3 is completely rewritten with ES2015 features like arrow functions, TextDecoder and TextEncoder. All modern browsers and node 12 or up are directly supported. Your codes should run unchanged. IE is no longer supported directly but you can transpile the script to use it (see below).

The hardest part of maintaing this module was not Base64 features, but cross-platform support (eg. nodejs vs web browsers). By making ES2015 mandatory virtually all codes are common (except atob() and btoa()).

If you need to support legacy browsers like IE, use version 2.

Ironically ES6 export is not used to keep the API compatible.

Old MS Edge workaround

MS Edge before 79 MS Edge before 79 (before Chromium) lacks TextEncoder and TextDecoder. textencoding.js is provided to polyfill those missing constructors. Load it ahead of base64.js .

Usage

Install

$ npm install --save js-base64

Transpile to ES5

Since base64.js is now written in ES2015 (aka ES6), It no longer runs on IE. Yet you can still transpile it to ES5 and the resulting script does run on IE. just

$ npm run build

which does

$ babel base64.js -o base64-es5.js

In Browser

Locally…

<!-- 
    MS Edge before 79 (before Chromium) lacks TextEncoder and TextDecoder.
    You can polyfill them by loading textencoding.js before base64.js
-->
<script src="textencoding.js"></script>
<script src="base64.js"></script>

… or Directly from CDN. In which case you don't even need to install.

<script src="https://cdn.jsdelivr.net/npm/js-base64@3.0.2/textencoding.min.js">
<script src="https://cdn.jsdelivr.net/npm/js-base64@3.0.2/base64.min.js">

node.js

const Base64 = require('js-base64').Base64;

As a ES6 Module (via babel, et al.)

import { Base64 } from 'js-base64';

SYNOPSIS

Base64.encode('dankogai'); // ZGFua29nYWk=
Base64.btoa(  'dankogai'); // ZGFua29nYWk=
Base64.fromUint8Array(     // ZGFua29nYWk=
    new Uint8Array([100,97,110,107,111,103,97,105])
);
Base64.fromUint8Array(     // ZGFua29nYW which is URI safe
    new Uint8Array([100,97,110,107,111,103,97,105]), true
);
Base64.encode(   '小飼弾'); // 5bCP6aO85by+
Base64.encodeURI('小飼弾'); // 5bCP6aO85by- which equals to Base64.encode('小飼弾', true)
Base64.btoa(     '小飼弾'); // raises exception 

Base64.decode('ZGFua29nYWk=');  // dankogai
Base64.atob(  'ZGFua29nYWk=');  // dankogai
Base64.toUint8Array(            // new Uint8Array([100,97,110,107,111,103,97,105])
    'ZGFua29nYWk='
);
Base64.decode('5bCP6aO85by+');  // 小飼弾
// note .decodeURI() is unnecessary since it accepts both flavors
Base64.decode('5bCP6aO85by-');  // 小飼弾
Base64.atob(  '5bCP6aO85by+');  // '小飼弾' which is nonsense

String Extension for ES5

// you have to explicitly extend String.prototype
Base64.extendString();
// once extended, you can do the following
'dankogai'.toBase64();        // ZGFua29nYWk=
'小飼弾'.toBase64();           // 5bCP6aO85by+
'小飼弾'.toBase64(true);       // 5bCP6aO85by-
'小飼弾'.toBase64URI();        // 5bCP6aO85by-
'小飼弾'.toBase64URL();        // 5bCP6aO85by- an alias of .toBase64URI()
'ZGFua29nYWk='.fromBase64();  // dankogai
'5bCP6aO85by+'.fromBase64();  // 小飼弾
'5bCP6aO85by-'.fromBase64();  // 小飼弾
'5bCP6aO85by-'.toUint8Array();// new Uint8Array([100,97,110,107,111,103,97,105])

// you have to explicitly extend String.prototype
Base64.extendString();
// once extended, you can do the following
const u8s =  new Uint8Array([100,97,110,107,111,103,97,105]);
u8s.toBase64();     // 'ZGFua29nYWk='
u8s.toBase64URI();  // 'ZGFua29nYWk'
u8s.toBase64URL();  // 'ZGFua29nYWk' an alias of .toBase64URI()

You can extend both via Base64.extendBuiltin().

TypeScript

TypeScript 2.0 type definition was added to the DefinitelyTyped repository.

$ npm install --save @types/js-base64

.decode() vs .atob (and .encode() vs btoa())

Suppose you have:

var pngBase64 = 
  "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII=";

Which is a Base64-encoded 1x1 transparent PNG, DO NOT USE Base64.decode(pngBase64).  Use Base64.atob(pngBase64) instead.  Base64.decode() decodes to UTF-8 string while Base64.atob() decodes to bytes, which is compatible to browser built-in atob() (Which is absent in node.js).  The same rule applies to the opposite direction.

Or even better, Base64.toUint8Array(pngBase64).

SEE ALSO

• http://en.wikipedia.org/wiki/Base64