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# base64.js
Yet another [Base64] transcoder.
[Base64]: http://en.wikipedia.org/wiki/Base64
## Install
```shell
$ npm install --save js-base64
```
## Usage
### In Browser
Locally…
```html
```
… or Directly from CDN. In which case you don't even need to install.
```html
```
This good old way loads `Base64` in the global context (`window`). Though `Base64.noConflict()` is made available, you should consider using ES6 Module to avoid tainting `window`.
### As an ES6 Module
locally…
```javascript
import { Base64 } from 'js-base64';
```
```javascript
// or if you prefer no Base64 namespace
import { encode, decode } from 'js-base64';
```
or even remotely.
```html
```
```html
```
### node.js (commonjs)
```javascript
const {Base64} = require('js-base64');
```
Unlike the case above, the global context is no longer modified.
You can also use [esm] to `import` instead of `require`.
[esm]: https://github.com/standard-things/esm
```javascript
require=require('esm')(module);
import {Base64} from 'js-base64';
```
## SYNOPSIS
```javascript
let latin = 'dankogai';
let utf8 = '小飼弾'
let u8s = new Uint8Array([100,97,110,107,111,103,97,105]);
Base64.encode(latin); // ZGFua29nYWk=
Base64.encode(latin, true); // ZGFua29nYWk skips padding
Base64.encodeURI(latin); // ZGFua29nYWk
Base64.btoa(latin); // ZGFua29nYWk=
Base64.btoa(utf8); // raises exception
Base64.fromUint8Array(u8s); // ZGFua29nYWk=
Base64.fromUint8Array(u8s, true); // ZGFua29nYW which is URI safe
Base64.encode(utf8); // 5bCP6aO85by+
Base64.encode(utf8, true) // 5bCP6aO85by-
Base64.encodeURI(utf8); // 5bCP6aO85by-
```
```javascript
Base64.decode( 'ZGFua29nYWk=');// dankogai
Base64.decode( 'ZGFua29nYWk'); // dankogai
Base64.atob( 'ZGFua29nYWk=');// dankogai
Base64.atob( '5bCP6aO85by+');// 'å°é£¼å¼¾' which is nonsense
Base64.toUint8Array('ZGFua29nYWk=');// u8s above
Base64.decode( '5bCP6aO85by+');// 小飼弾
// note .decodeURI() is unnecessary since it accepts both flavors
Base64.decode( '5bCP6aO85by-');// 小飼弾
```
```javascript
Base64.isValid(0); // false: 0 is not string
Base64.isValid(''); // true: a valid Base64-encoded empty byte
Base64.isValid('ZA=='); // true: a valid Base64-encoded 'd'
Base64.isValid('Z A='); // true: whitespaces are okay
Base64.isValid('ZA'); // true: padding ='s can be omitted
Base64.isValid('++'); // true: can be non URL-safe
Base64.isValid('--'); // true: or URL-safe
Base64.isValid('+-'); // false: can't mix both
```
### Built-in Extensions
By default `Base64` leaves built-in prototypes untouched. But you can extend them as below.
```javascript
// 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- ab alias of .toBase64(true)
'小飼弾'.toBase64URL(); // 5bCP6aO85by- an alias of .toBase64URI()
'ZGFua29nYWk='.fromBase64(); // dankogai
'5bCP6aO85by+'.fromBase64(); // 小飼弾
'5bCP6aO85by-'.fromBase64(); // 小飼弾
'5bCP6aO85by-'.toUint8Array();// u8s above
```
```javascript
// you have to explicitly extend Uint8Array.prototype
Base64.extendUint8Array();
// once extended, you can do the following
u8s.toBase64(); // 'ZGFua29nYWk='
u8s.toBase64URI(); // 'ZGFua29nYWk'
u8s.toBase64URL(); // 'ZGFua29nYWk' an alias of .toBase64URI()
```
```javascript
// extend all at once
Base64.extendBuiltins()
```
## `.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)`.
## Brief History
* Since version 3.3 it is written in TypeScript. Now `base64.mjs` is compiled from `base64.ts` then `base64.js` is generated from `base64.mjs`.
* Since version 3.7 `base64.js` is ES5-compatible again (hence IE11-compatible).
* Since 3.0 `js-base64` switch to ES2015 module so it is no longer compatible with legacy browsers like IE (see above)