浏览器中DOMString是UTF-16编码. 如果输入字符串中包含超过8位(0x00~0xFF)的字符, 就会报这个错误.

思路一

对整个字符串进行转义(如使用encodeURIComponent 进行UTF-8转义)然后再btoa编码.

let Base64 = {

    encode(str) {

        // first we use encodeURIComponent to get percent-encoded UTF-8,

        // then we convert the percent encodings into raw bytes which

        // can be fed into btoa.

        return btoa(encodeURIComponent(str).replace(/%([-9A-F]{})/g,

            function toSolidBytes(match, p1) {

                return String.fromCharCode('0x' + p1);

            }));

    },

    decode(str) {

        // Going backwards: from bytestream, to percent-encoding, to original string.

        return decodeURIComponent(atob(str).split('').map(function (c) {

            return '%' + ('' + c.charCodeAt().toString()).slice(-);

        }).join(''));

    }

};

let encoded = Base64.encode("哈ha"); // "5ZOIaGE="

let decoded = Base64.decode(encoded); // "哈ha"

/**

*

*  Base64 encode / decode

*  http://www.webtoolkit.info

*

**/

var Base64 = {

    // private property

    _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="

    // public method for encoding

    , encode: function (input)

    {

        var output = "";

        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;

        var i = ;

        input = Base64._utf8_encode(input);

        while (i < input.length)

        {

            chr1 = input.charCodeAt(i++);

            chr2 = input.charCodeAt(i++);

            chr3 = input.charCodeAt(i++);

            enc1 = chr1 >> ;

            enc2 = ((chr1 & ) << ) | (chr2 >> );

            enc3 = ((chr2 & ) << ) | (chr3 >> );

            enc4 = chr3 & ;

            if (isNaN(chr2))

            {

                enc3 = enc4 = ;

            }

            else if (isNaN(chr3))

            {

                enc4 = ;

            }

            output = output +

                this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +

                this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);

        } // Whend 

        return output;

    } // End Function encode 

    // public method for decoding

    ,decode: function (input)

    {

        var output = "";

        var chr1, chr2, chr3;

        var enc1, enc2, enc3, enc4;

        var i = ;

        input = input.replace(/[^A-Za-z0-\+\/\=]/g, "");

        while (i < input.length)

        {

            enc1 = this._keyStr.indexOf(input.charAt(i++));

            enc2 = this._keyStr.indexOf(input.charAt(i++));

            enc3 = this._keyStr.indexOf(input.charAt(i++));

            enc4 = this._keyStr.indexOf(input.charAt(i++));

            chr1 = (enc1 << ) | (enc2 >> );

            chr2 = ((enc2 & ) << ) | (enc3 >> );

            chr3 = ((enc3 & ) << ) | enc4;

            output = output + String.fromCharCode(chr1);

            if (enc3 != )

            {

                output = output + String.fromCharCode(chr2);

            }

            if (enc4 != )

            {

                output = output + String.fromCharCode(chr3);

            }

        } // Whend 

        output = Base64._utf8_decode(output);

        return output;

    } // End Function decode 

    // private method for UTF-8 encoding

    ,_utf8_encode: function (string)

    {

        var utftext = "";

        string = string.replace(/\r\n/g, "\n");

        for (var n = ; n < string.length; n++)

        {

            var c = string.charCodeAt(n);

            if (c < )

            {

                utftext += String.fromCharCode(c);

            }

            else if ((c > ) && (c < ))

            {

                utftext += String.fromCharCode((c >> ) | );

                utftext += String.fromCharCode((c & ) | );

            }

            else

            {

                utftext += String.fromCharCode((c >> ) | );

                utftext += String.fromCharCode(((c >> ) & ) | );

                utftext += String.fromCharCode((c & ) | );

            }

        } // Next n 

        return utftext;

    } // End Function _utf8_encode 

    // private method for UTF-8 decoding

    ,_utf8_decode: function (utftext)

    {

        var string = "";

        var i = ;

        var c, c1, c2, c3;

        c = c1 = c2 = ;

        while (i < utftext.length)

        {

            c = utftext.charCodeAt(i);

            if (c < )

            {

                string += String.fromCharCode(c);

                i++;

            }

            else if ((c > ) && (c < ))

            {

                c2 = utftext.charCodeAt(i + );

                string += String.fromCharCode(((c & ) << ) | (c2 & ));

                i += ;

            }

            else

            {

                c2 = utftext.charCodeAt(i + );

                c3 = utftext.charCodeAt(i + );

                string += String.fromCharCode(((c & ) << ) | ((c2 & ) << ) | (c3 & ));

                i += ;

            }

        } // Whend 

        return string;

    } // End Function _utf8_decode 

}