Base64

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);
3. Base64编/解码本该与字符串无关, 但现有库几乎只支持字符串;
4. 能用上Tree-shaking, 项目一般只用需要(encode 或 decode), 我可不想copy代码;
5. 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;
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

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;

API

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;