js specified number of incremental technology base64 encryption and decryption

var Base = new new the Base64 ();
 var STR = 'userzl271_123456_143882372' ; 
 var code =. 8;   // constant 
var Result = encode (base.encode (STR), code);   // Base incremented eight encryption 
console.log (result );   

var result2 = base.decode (decode (Result, code));   // Base incremental decrypted 8 
the console.log (result2); 


// encryption, decryption algorithm package: 
function encode (Content, code) {
     var STR = '' ;
     for ( var I = 0; I <content.length; I ++ ) {
         var calAscii = content.charCodeAt(i);
        if(calAscii>=65 && calAscii<=90){
            calAscii += code;
            if(calAscii > 90) calAscii -= 26;
        }
        if(calAscii>=97 && calAscii<=122){
            calAscii += code;
            if(calAscii > 122)  calAscii -= 26;
        }
        str += String.fromCharCode(calAscii);
    }
    return str;
}

function decode(result, code){
    str = '';
    for(var i = 0; the <result.length; i ++ ) {
         var calAscii = result.charCodeAt (i);
        if (calAscii> = 65 && calAscii <= 90 ) { 
            calAscii - = code;
            if (calAscii <65) calAscii + = 26 ; 
        } 
        If (calAscii> = 97 && calAscii <= 122 ) { 
            calAscii - = code;
            if (calAscii <97) calAscii + = 26 ; 
        } 

        Str + = String.fromCharCode (calAscii); 
    } 
    Return str; 
} 

function Base64() {  

    // private property  
    _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";  

    // public method for encoding  
    this.encode = function (input) {  
        var output = "";  
        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;  
        var i = 0;  
        input = _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;  
    }  

    // public method for decoding  
    this.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 = _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 = _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;  
    }  
}