encode(input) {   //編碼方法
            var _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
            var output = "";
            var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
            var i = 0;
            input = this._utf8_encode(input);
            while (i < input.length) {
                chr1 = input.charCodeAt(i++);
                chr2 = input.charCodeAt(i++);
                chr3 = input.charCodeAt(i++);
                enc1 = chr1 >> 2;
                enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
                enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
                enc4 = chr3 & 63;
                if (isNaN(chr2)) {
                    enc3 = enc4 = 64;
                } else if (isNaN(chr3)) {
                    enc4 = 64;
                }
                output = output +
                _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
                _keyStr.charAt(enc3) + _keyStr.charAt(enc4);
            }
            return output;
        },
        decode(input) {    //解碼方法
            var _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
            var output = "";
            var chr1, chr2, chr3;
            var enc1, enc2, enc3, enc4;
            var i = 0;
            input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
            while (i < input.length) {
                enc1 = _keyStr.indexOf(input.charAt(i++));
                enc2 = _keyStr.indexOf(input.charAt(i++));
                enc3 = _keyStr.indexOf(input.charAt(i++));
                enc4 = _keyStr.indexOf(input.charAt(i++));
                chr1 = (enc1 << 2) | (enc2 >> 4);
                chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
                chr3 = ((enc3 & 3) << 6) | enc4;
                output = output + String.fromCharCode(chr1);
                if (enc3 != 64) {
                    output = output + String.fromCharCode(chr2);
                }
                if (enc4 != 64) {
                    output = output + String.fromCharCode(chr3);
                }
            }
            output = this._utf8_decode
 
(output);
            return output;
        },
        _utf8_encode(string) {
            string = string.replace(/\r\n/g,"\n");
            var utftext = "";
            for (var n = 0; n < string.length; n++) {
                var c = string.charCodeAt(n);
                if (c < 128) {
                    utftext += String.fromCharCode(c);
                } else if((c > 127) && (c < 2048)) {
                    utftext += String.fromCharCode((c >> 6) | 192);
                    utftext += String.fromCharCode((c & 63) | 128);
                } else {
                    utftext += String.fromCharCode((c >> 12) | 224);
                    utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                    utftext += String.fromCharCode((c & 63) | 128);
                }
            }
            return utftext;
        },
        _utf8_decode(utftext) {
            var string = "";
            var i = 0;
            var c,c1,c2,c3 = 0;
            while ( i < utftext.length ) {
                c = utftext.charCodeAt(i);
                if (c < 128) {
                    string += String.fromCharCode(c);
                    i++;
                } else if((c > 191) && (c < 224)) {
                    c2 = utftext.charCodeAt(i+1);
                    string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
                    i += 2;
                } else {
                    c2 = utftext.charCodeAt(i+1);
                    c3 = utftext.charCodeAt(i+2);
                    string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
                    i += 3;
                }
            }
            return string;
        },
 

字串型別的可以直接編碼，

而json，需要先使用JSON.stringgify()方法轉化成字串型，然後編碼

我的程式碼是在vue環境中的，所以有很多呼叫都是this.方法名(我有標紅加粗)，具體環境不一樣，可以自己做修改。

        var aaa = {
            "a": 'a',
            "b": "bb",
            "c": "ccc"
        }
        var string = JSON.stringify(aaa);
        console.dir( "編碼："+this.encode(string)  )
        console.dir( "解碼："+this.decode
 
(this.base64_encode(string)) );

關於編碼的另外一個方法，只一個方法就可以，沒那麼囉嗦

同樣的，字串型別的可以直接編碼，

而json，需要先使用JSON.stringgify()方法轉化成字串型，然後編碼

        base64_encode(str) {    // 編碼
            // 編碼檔案
            var c1, c2, c3;
            var base64EncodeChars =
                "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
            var i = 0,
                len = str.length,
                string = "";
            while (i < len) {
                c1 = str.charCodeAt(i++) & 0xff;
                if (i == len) {
                    string += base64EncodeChars.charAt(c1 >> 2);
                    string += base64EncodeChars.charAt((c1 & 0x3) << 4);
                    string += "==";
                    break;
                }
                c2 = str.charCodeAt(i++);
                if (i == len) {
                    string += base64EncodeChars.charAt(c1 >> 2);
                    string += base64EncodeChars.charAt(
                        ((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4)
                    );
                    string += base64EncodeChars.charAt((c2 & 0xf) << 2);
                    string += "=";
                    break;
                }
                c3 = str.charCodeAt(i++);
                string += base64EncodeChars.charAt(c1 >> 2);
                string += base64EncodeChars.charAt(
                    ((c1 & 0x3) << 4) | ((c2 & 0xf0) >> 4)
                );
                string += base64EncodeChars.charAt(
                    ((c2 & 0xf) << 2) | ((c3 & 0xc0) >> 6)
                );
                string += base64EncodeChars.charAt(c3 & 0x3f);
            }
            return string;
        }