1  # abab [![npm version](https://badge.fury.io/js/abab.svg)](https://www.npmjs.com/package/abab) [![Build Status](https://travis-ci.org/jsdom/abab.svg?branch=master)](https://travis-ci.org/jsdom/abab)
 2  
 3  A JavaScript module that implements `window.atob` and `window.btoa` according the forgiving-base64 algorithm in the [Infra Standard](https://infra.spec.whatwg.org/#forgiving-base64). The original code was forked from [w3c/web-platform-tests](https://github.com/w3c/web-platform-tests/blob/master/html/webappapis/atob/base64.html).
 4  
 5  Compatibility: Node.js version 3+ and all major browsers.
 6  
 7  Install with `npm`:
 8  
 9  ```sh
10  npm install abab
11  ```
12  
13  ## API
14  
15  ### `btoa` (base64 encode)
16  
17  ```js
18  const { btoa } = require('abab');
19  btoa('Hello, world!'); // 'SGVsbG8sIHdvcmxkIQ=='
20  ```
21  
22  ### `atob` (base64 decode)
23  
24  ```js 
25  const { atob } = require('abab');
26  atob('SGVsbG8sIHdvcmxkIQ=='); // 'Hello, world!'
27  ```
28  
29  #### Valid characters
30  
31  [Per the spec](https://html.spec.whatwg.org/multipage/webappapis.html#atob:dom-windowbase64-btoa-3), `btoa` will accept strings "containing only characters in the range `U+0000` to `U+00FF`." If passed a string with characters above `U+00FF`, `btoa` will return `null`. If `atob` is passed a string that is not base64-valid, it will also return `null`. In both cases when `null` is returned, the spec calls for throwing a `DOMException` of type `InvalidCharacterError`.
32  
33  ## Browsers
34  
35  If you want to include just one of the methods to save bytes in your client-side code, you can `require` the desired module directly.
36  
37  ```js
38  const atob = require('abab/lib/atob');
39  const btoa = require('abab/lib/btoa');
40  ```
41  
42  ## Development
43  
44  If you're **submitting a PR** or **deploying to npm**, please use the [checklists in CONTRIBUTING.md](CONTRIBUTING.md#checklists).
45  
46  ## Remembering what `atob` and `btoa` stand for
47  
48  Base64 comes from IETF [RFC 4648](https://tools.ietf.org/html/rfc4648#section-4) (2006). 
49  
50  - **`btoa`**, the encoder function, stands for **binary** to **ASCII**, meaning it converts any binary input into a subset of **ASCII** (Base64).
51  - **`atob`**, the decoder function, converts **ASCII** (or Base64) to its original **binary** format.