170 lines
5.2 KiB
Markdown
170 lines
5.2 KiB
Markdown
[](https://github.com/dankogai/js-base64/actions/workflows/node.js.yml)
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# base64.js
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Yet another [Base64] transcoder.
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[Base64]: http://en.wikipedia.org/wiki/Base64
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## Install
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```shell
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$ npm install --save js-base64
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```
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## Usage
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### In Browser
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Locally…
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```html
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<script src="base64.js"></script>
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```
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… or Directly from CDN. In which case you don't even need to install.
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```html
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<script src="https://cdn.jsdelivr.net/npm/js-base64@3.7.7/base64.min.js"></script>
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```
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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`.
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### As an ES6 Module
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locally…
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```javascript
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import { Base64 } from 'js-base64';
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```
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```javascript
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// or if you prefer no Base64 namespace
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import { encode, decode } from 'js-base64';
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```
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or even remotely.
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```html
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<script type="module">
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// note jsdelivr.net does not automatically minify .mjs
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import { Base64 } from 'https://cdn.jsdelivr.net/npm/js-base64@3.7.7/base64.mjs';
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</script>
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```
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```html
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<script type="module">
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// or if you prefer no Base64 namespace
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import { encode, decode } from 'https://cdn.jsdelivr.net/npm/js-base64@3.7.7/base64.mjs';
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</script>
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```
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### node.js (commonjs)
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```javascript
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const {Base64} = require('js-base64');
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```
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Unlike the case above, the global context is no longer modified.
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You can also use [esm] to `import` instead of `require`.
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[esm]: https://github.com/standard-things/esm
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```javascript
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require=require('esm')(module);
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import {Base64} from 'js-base64';
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```
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## SYNOPSIS
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```javascript
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let latin = 'dankogai';
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let utf8 = '小飼弾'
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let u8s = new Uint8Array([100,97,110,107,111,103,97,105]);
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Base64.encode(latin); // ZGFua29nYWk=
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Base64.encode(latin, true); // ZGFua29nYWk skips padding
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Base64.encodeURI(latin); // ZGFua29nYWk
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Base64.btoa(latin); // ZGFua29nYWk=
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Base64.btoa(utf8); // raises exception
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Base64.fromUint8Array(u8s); // ZGFua29nYWk=
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Base64.fromUint8Array(u8s, true); // ZGFua29nYW which is URI safe
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Base64.encode(utf8); // 5bCP6aO85by+
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Base64.encode(utf8, true) // 5bCP6aO85by-
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Base64.encodeURI(utf8); // 5bCP6aO85by-
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```
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```javascript
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Base64.decode( 'ZGFua29nYWk=');// dankogai
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Base64.decode( 'ZGFua29nYWk'); // dankogai
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Base64.atob( 'ZGFua29nYWk=');// dankogai
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Base64.atob( '5bCP6aO85by+');// 'å°é£¼å¼¾' which is nonsense
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Base64.toUint8Array('ZGFua29nYWk=');// u8s above
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Base64.decode( '5bCP6aO85by+');// 小飼弾
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// note .decodeURI() is unnecessary since it accepts both flavors
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Base64.decode( '5bCP6aO85by-');// 小飼弾
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```
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```javascript
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Base64.isValid(0); // false: 0 is not string
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Base64.isValid(''); // true: a valid Base64-encoded empty byte
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Base64.isValid('ZA=='); // true: a valid Base64-encoded 'd'
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Base64.isValid('Z A='); // true: whitespaces are okay
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Base64.isValid('ZA'); // true: padding ='s can be omitted
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Base64.isValid('++'); // true: can be non URL-safe
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Base64.isValid('--'); // true: or URL-safe
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Base64.isValid('+-'); // false: can't mix both
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```
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### Built-in Extensions
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By default `Base64` leaves built-in prototypes untouched. But you can extend them as below.
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```javascript
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// you have to explicitly extend String.prototype
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Base64.extendString();
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// once extended, you can do the following
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'dankogai'.toBase64(); // ZGFua29nYWk=
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'小飼弾'.toBase64(); // 5bCP6aO85by+
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'小飼弾'.toBase64(true); // 5bCP6aO85by-
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'小飼弾'.toBase64URI(); // 5bCP6aO85by- ab alias of .toBase64(true)
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'小飼弾'.toBase64URL(); // 5bCP6aO85by- an alias of .toBase64URI()
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'ZGFua29nYWk='.fromBase64(); // dankogai
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'5bCP6aO85by+'.fromBase64(); // 小飼弾
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'5bCP6aO85by-'.fromBase64(); // 小飼弾
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'5bCP6aO85by-'.toUint8Array();// u8s above
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```
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```javascript
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// you have to explicitly extend Uint8Array.prototype
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Base64.extendUint8Array();
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// once extended, you can do the following
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u8s.toBase64(); // 'ZGFua29nYWk='
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u8s.toBase64URI(); // 'ZGFua29nYWk'
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u8s.toBase64URL(); // 'ZGFua29nYWk' an alias of .toBase64URI()
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```
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```javascript
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// extend all at once
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Base64.extendBuiltins()
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```
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## `.decode()` vs `.atob` (and `.encode()` vs `btoa()`)
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Suppose you have:
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```
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var pngBase64 =
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"iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII=";
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```
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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.
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Or even better, `Base64.toUint8Array(pngBase64)`.
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## Brief History
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* 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`.
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* Since version 3.7 `base64.js` is ES5-compatible again (hence IE11-compatible).
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* Since 3.0 `js-base64` switch to ES2015 module so it is no longer compatible with legacy browsers like IE (see above)
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