base64 数据加密

1.新建一个base64.js文件 添加下面的代码

/* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
 * Version: 1.0
 * LastModified: Dec 25 1999
 * This library is free. You can redistribute it and/or modify it.
 */

/*
 * Interfaces:
 * b64 = base64encode(data);
 * data = base64decode(b64);
 */

var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
var base64DecodeChars = new Array(-, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, -, , -, -, -, ,
    , , , , , , , , , , -, -, -, -, -, -, -, , , , , , , , , , , , , , , ,
    , , , , , , , , , , , -, -, -, -, -, -, , , , , , , , , , , , , , , ,
    , , , , , , , , , , , -, -, -, -, -);

function base64encode(str) {
    var out, i, len;
    var c1, c2, c3;

    len = str.length;
    i = ;
    out = "";
    while (i < len) {
        c1 = str.charCodeAt(i++) & 0xff;
        if (i == len) {
            out += base64EncodeChars.charAt(c1 >> );
            out += base64EncodeChars.charAt((c1 & 0x3) << );
            out += "==";
            break;
        }
        c2 = str.charCodeAt(i++);
        if (i == len) {
            out += base64EncodeChars.charAt(c1 >> );
            out += base64EncodeChars.charAt(((c1 & 0x3) << ) | ((c2 & 0xF0) >> ));
            out += base64EncodeChars.charAt((c2 & 0xF) << );
            out += "=";
            break;
        }
        c3 = str.charCodeAt(i++);
        out += base64EncodeChars.charAt(c1 >> );
        out += base64EncodeChars.charAt(((c1 & 0x3) << ) | ((c2 & 0xF0) >> ));
        out += base64EncodeChars.charAt(((c2 & 0xF) << ) | ((c3 & 0xC0) >> ));
        out += base64EncodeChars.charAt(c3 & 0x3F);
    }
    return out;
}

function base64decode(str) {
    var c1, c2, c3, c4;
    var i, len, out;

    len = str.length;
    i = ;
    out = "";
    while (i < len) {
        /* c1 */
        do {
            c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
        } while (i < len && c1 == -);
        if (c1 == -)
            break;

        /* c2 */
        do {
            c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff];
        } while (i < len && c2 == -);
        if (c2 == -)
            break;

        out += String.fromCharCode((c1 << ) | ((c2 & 0x30) >> ));

        /* c3 */
        do {
            c3 = str.charCodeAt(i++) & 0xff;
            if (c3 == )
                return out;
            c3 = base64DecodeChars[c3];
        } while (i < len && c3 == -);
        if (c3 == -)
            break;

        out += String.fromCharCode(((c2 & 0XF) << ) | ((c3 & 0x3C) >> ));

        /* c4 */
        do {
            c4 = str.charCodeAt(i++) & 0xff;
            if (c4 == )
                return out;
            c4 = base64DecodeChars[c4];
        } while (i < len && c4 == -);
        if (c4 == -)
            break;
        out += String.fromCharCode(((c3 & 0x03) << ) | c4);
    }
    return out;
}

上面代码中的base64encode()用于编码，base64decode()用于解码。
2.在前段导入 base64.js文件

<script type="text/javascript" src="md5/base64.js"></script>

3.加密

function aa(){
      sEncoded=base64encode("aa");
      alert(sEncoded)
    }

4.解密

function bb(){
      sDecoded=base64decode("YWE=");
      alert(sDecoded)
    }

5.对utf-8字符进行编码要这样写：

sEncoded=base64encode(utf16to8(str));

然后，解码要这样写：

sDecoded=utf8to16(base64decode(sEncoded))

参考文献：
http://www.ruanyifeng.com/blog/2008/06/base64.html
测试
https://jsfiddle.net/gabrieleromanato/qAGHT/