# Base64.js

**Repository Path**: cnwhy/Base64.js

## Basic Information

- **Project Name**: Base64.js
- **Description**: Base64 library, lossless transcoding.
- **Primary Language**: JavaScript
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2019-06-10
- **Last Updated**: 2020-12-17

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Base64
[![Build Status](https://travis-ci.org/cnwhy/Base64.js.svg?branch=master)](https://travis-ci.org/cnwhy/Base64.js)
[![Coverage Status](https://coveralls.io/repos/github/cnwhy/Base64.js/badge.svg?branch=master)](https://coveralls.io/github/cnwhy/Base64.js?branch=master)  
> **Base64** `编码`,`解码` 库;

## 适用场景

- 二进制数据与 Base64 互转
- 字符串与 Base64 互转

## install
```
npm i @cnwhy/base64
```

## 为何重复造轮子?
1. 需要单纯的Base64的库,而且能在浏览器上使用; (利用node的 `Buffer` 对像的方法出局)
2. 支持字符串; (`btoa` , `atob` 只支持 [Latin1](https://zh.wikipedia.org/wiki/ISO/IEC_8859-1));
4. `Base64`编/解码本该与字符串无关, 但现有库几乎只支持字符串;
5. 能用上`Tree-shaking`, 项目一般只用需要(`encode` 或 `decode`), 我可不想copy代码;
3. javascript 字符串无损转换 (因为这一点, 现有库几乎全军覆没), [具体例子](https://github.com/cnwhy/Base64.js/wiki/javascript%E5%AD%97%E7%AC%A6%E4%B8%B2%E6%97%A0%E6%8D%9F%E8%BD%AC%E6%8D%A2%E6%8E%A2%E8%AE%A8);
6. 能应付异型`Base64`方案;

## 兼容性
通用, 对于不支持`ArrayBuffer`的环境将会用`Array`代替`Uint8Array`.

## 使用
```js
const { encode, decode, createEncode, createDecode } = require('@cnwhy/base64');
// import { encode, decode, createEncode, createDecode } from '@cnwhy/base64';

// 1. 字符串 
let str = '中国𐄡美国';
let b64 = encode(str);
console.log(b64);
let _str = decode(b64).toString(); // 必须调用toString()方法还原为字符串.
console.log('string:', str === _str);  // true

// 2. 字节数组
// let buffer = fs.readFileSync('./test.js');
let buffer = new Uint8Array([0,255,127,33,0,5]);
let fb64 = encode(buffer); // encode支持 Buffer , Stirng, Array<number>
let fu8arr = decode(fb64); // decode 返回Uint8Array对像
console.log('buffer:', Array.from(buffer).join() == Array.from(fu8arr).join());

// 3. 自定义 Base64 转换方法

// 自定义码表与补位符
const TABLE = 'xQh}s7*y~A|nkj4Bf%z1R,P+)mMS{(&EWCKegp6r!OX</LuY-l9^ZJ#cTU[vHda$'; 
const PAD = '.'; 

// 自定义字符串编码/解码方法
const Utf16Encode = function(str) {
	let cods = str.split('').map(s => s.charCodeAt(0));
	return new Uint8Array(new Uint16Array(cods).buffer);
}
const Utf16Decode = function(arr) {
	let u16 = Array.from(new Uint16Array(arr.buffer));
	return u16.map(c => String.fromCharCode(c)).join('');
}

//创建自定义转码函数
const myEncode = createEncode(TABLE,PAD,Utf16Encode);
const myDecode = createDecode(TABLE,PAD,Utf16Decode);

console.log('\n自定义转码:');
let myb64 = myEncode(str);
console.log(myb64);
let my_str = myDecode(myb64).toString(); // 调用toString() 会用 Utf16Decode 方法将字节数组转为字符串
console.log('my:',str == my_str);

//output:
/*
5Lit5Zu98JCEoee+juWbvQ==
string: true
buffer: true

自定义转码:
nRvd,W})~(#4E$JP
my: true
*/
```
> 更多使用例子可以参看[这篇](https://blog.whyoop.com/2019/06/03/new-base64/#demo);

## API

```ts
Base64 = {
	BASE64_TABLE: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	BASE64_URL_TABLE: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
	PAD: "=";
	// UTF8 编码 解码; 可做为 strEncode strDecode 参数;
	utf8Encode(str:string):Uint8Array|number[];
	utf8Decode(utf8arr:Uint8Array|number[]):string;

	//Base64 编码 解码
	encode(input:string|ArrayBuffer|Uint8Array|number[]):string;
	decode(base64str: string) => number[]|Uint8Array;

	//适用于URL的Base64 编码 解码( "_" "-" 替换 "/" "+");
	encodeURL(input:string|ArrayBuffer|Uint8Array|number[]):string;
	decodeURL(base64str: string) => number[]|Uint8Array;

	//创建自定义Base64 encode , decode 函数
	createEncode(strEncode: Function): (input: any) => string;
	createEncode(table?: string[] | string, pad?: string, strEncode?: Function): (input: any) => string;
	createDecode(strDecode: Function): (base64str: string) => Uint8Array | number[];
	createDecode(table?: string[] | string, pad?: string, strDecode?: Function): (base64str: string) => Uint8Array | number[];
}
```

## 参考资料
[https://tools.ietf.org/html/rfc4648](https://tools.ietf.org/html/rfc4648);