const charset = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

const paddingChar = '=';

function encode(input) {

    const paddings = 3 - (input.length % 3 || 3);

    let encoded = '';

    let binaries = '';

    for (let i = 0; i < input.length + paddings; i++) {

        const char = input[i];

        const binary = char ? char.charCodeAt(0).toString(2).padStart(8, '0') : '00000000';

        // the binaries length could only be 0, 2 or 4 because the bits will be consumed once become 6

        switch (binaries.length) {

            case 0:

                encoded += charset[parseInt(binary.slice(0, 6), 2)];

                binaries = binary.slice(6);

                break;

            case 2:

                encoded += charset[parseInt(`${binaries}${binary.slice(0, 4)}`, 2)];

                binaries = binary.slice(4);

                break;

            case 4:

                // the paddings count could only be 0, 1 or 2

                switch (paddings) {

                    case 0:

                        encoded += charset[parseInt(`${binaries}${binary.slice(0, 2)}`, 2)];

                        encoded += charset[parseInt(binary.slice(2), 2)];

                        break;

                    case 1:

                        // when there's only one padding and current char is undedefined (exceeded input string ranged)

                        // which means the last char is a padding char

                        if (!char) {

                            encoded += charset[parseInt(`${binaries}${binary.slice(0, 2)}`, 2)];

                            encoded += paddingChar;

                        }

                        else {

                            encoded += charset[parseInt(`${binaries}${binary.slice(0, 2)}`, 2)];

                            encoded += charset[parseInt(binary.slice(2), 2)];

                        }

                        break;

                    case 2:

                        // when there are 2 paddings and previous char is undedefined (exceeded input string ranged)

                        // which means the last 2 chars are padding chars

                        if (!input[i - 1]) {

                            encoded += paddingChar;

                            encoded += paddingChar;

                        }

                        else {

                            encoded += charset[parseInt(`${binaries}${binary.slice(0, 2)}`, 2)];

                            encoded += charset[parseInt(binary.slice(2), 2)];

                        }

                        break;

                }

                binaries = '';

                break;

        }

    }

    return encoded;

}

function decode(input) {

    let decoded = '';

    let binaries = '';

    for (let i = 0; i < input.length; i++) {

        const char = input[i];

        // once reached the padding char, don't need to continue the loop

        if (char === paddingChar) {

            break;

        }

        const code = charset.indexOf(char);

        const binary = code.toString(2).padStart(6, '0');

        // binaries length could only be 0, 2, 4 or 6 because the bits will be consumed once become 8

        switch (binaries.length) {

            case 0:

                binaries += binary;

                break;

            case 2:

                decoded += String.fromCharCode(parseInt(`${binaries}${binary}`, 2));

                binaries = '';

                break;

            case 4:

                decoded += String.fromCharCode(parseInt(`${binaries}${binary.slice(0, 4)}`, 2));

                binaries = binary.slice(4);

                break;

            case 6:

                decoded += String.fromCharCode(parseInt(`${binaries}${binary.slice(0, 2)}`, 2));

                binaries = binary.slice(2);

                break;

        }

    }

    return decoded;

}

​

var base64 = {

    encode,

    decode,

};

​

/**

*

*  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 = 0;

​

        input = Base64._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 +

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

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

        }

        return output;

    },

​

    // public method for decoding

    decode : function (input) {

        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 = 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 << 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 = Base64._utf8_decode(output);

​

        return output;

    },

​

    // private method for UTF-8 encoding

    _utf8_encode : function (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;

    },

​

    // private method for UTF-8 decoding

    _utf8_decode : function (utftext) {

        var string = "";

        var i = 0;

        var c = c1 = c2 = 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;

    }

}

​

var str = 'PYtFLbTaRSeG9qH781zL0d6irQoPYJDFT6ubjfXIAKfQEOXC';