前言

base64加密解密示例和代码：https://blog.csdn.net/weixin_43992507/article/details/108791605
使用jquery.base64.js解密时，中文出现乱码，如下处理

/**
 * --------------------------------------------------------------------------------------------------------------------
 * 解密例子
 */
function test(value) {
    
    
    // 解密前
    console.log("解密前", value)
    var data = $.base64.decode(value, "utf-8");// base64 解密
    console.log("解密后1【乱码】:", data)
    data = utf8To16(data); // 再次调用utf-8转utf-16即可转码成功
    console.log("解密后2【正常】:", data)
}

/**
 * --------------------------------------------------------------------------------------------------------------------
 * utf8转为utf16
 * @param str
 * @returns {string}
 */
function utf8To16(str) {
    
    
    var out, i, len, c;
    var char2, char3;
    out = "";
    len = str.length;
    i = 0;
    while (i < len) {
    
    
        c = str.charCodeAt(i++);
        switch (c >> 4) {
    
    
            case 0:
            case 1:
            case 2:
            case 3:
            case 4:
            case 5:
            case 6:
            case 7:
                // 0xxxxxxx
                out += str.charAt(i - 1);
                break;
            case 12:
            case 13:
                // 110x xxxx 10xx xxxx
                char2 = str.charCodeAt(i++);
                out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
                break;
            case 14:
                // 1110 xxxx 10xx xxxx 10xx xxxx
                char2 = str.charCodeAt(i++);
                char3 = str.charCodeAt(i++);
                out += String.fromCharCode(((c & 0x0F) << 12) |
                    ((char2 & 0x3F) << 6) |
                    ((char3 & 0x3F) << 0));
                break;
        }
    }
    return out;
}

/**
 * --------------------------------------------------------------------------------------------------------------------
 * utf16转为utf8
 * @param str
 * @returns {string}
 */
function utf16to8(str) {
    
    
    var out, i, len, c;
    out = "";
    len = str.length;
    for (i = 0; i < len; i++) {
    
    
        c = str.charCodeAt(i);
        if ((c >= 0x0001) && (c <= 0x007F)) {
    
    
            out += str.charAt(i);
        } else if (c > 0x07FF) {
    
    
            out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
            out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
            out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
        } else {
    
    
            out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
            out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
        }
    }
    return out;
}