What is the JavaScript equivalent of C#'s HttpServerUtility.UrlTokenDecode?

Question

In JavaScript, how can i decode a string that was encoded in C# using HttpServerUtility.UrlTokenEncode?

There are some equivalents in other languages but i couldn't rewrite them in JS. Any help would be appreciated.

This is the Java version.

This is the Objective-C version.

Update:

C#'s URLTokenEncode is not the same as base64 encoding. For example the last character is always the number of padding characters. So some characters need to be replaced properly. Java and Objective-C version of the code show which characters need to be replaced with what.

I tried decodeURIComponent but it was not decoded successfully. That makes sense because the string is encoded by a particular method. It's not base64.

For example, This is just a part of a C#'s UrlTokenEncode String:

vj4_fv7__7-_Pr6-ff3_Pr6_vz8_________________f____79_vP1_vb3_vz8____________________AAA1

And this is the correct decoded version using Objective-C/Java method:

vj4/fv7//7+/Pr6+ff3/Pr6/vz8/////////////////f////79/vP1/vb3/vz8////////////////////AAA=

Answer 1

I finally managed to convert the Objective-c version of URLTokenDecode by Jeffrey Thomas to JavaScript and it worked.

Here is the function:

function URLTokenDecode(token) {

    if (token.length == 0) return null;

    // The last character in the token is the number of padding characters.
    var numberOfPaddingCharacters = token.slice(-1);

    // The Base64 string is the token without the last character.
    token = token.slice(0, -1);

    // '-'s are '+'s and '_'s are '/'s.
    token = token.replace(/-/g, '+');
    token = token.replace(/_/g, '/');

    // Pad the Base64 string out with '='s
    for (var i = 0; i < numberOfPaddingCharacters; i++)
        token += "=";

    return token;
}

Here is the $filter if you are using AngularJS:

app.filter('URLTokenDecode', function () {
        return function (token) {

            if (token.length == 0) return null;

            // The last character in the token is the number of padding characters.
            var numberOfPaddingCharacters = token.slice(-1);

            // The Base64 string is the token without the last character.
            token = token.slice(0, -1);

            // '-'s are '+'s and '_'s are '/'s.
            token = token.replace(/-/g, '+');
            token = token.replace(/_/g, '/');

            // Pad the Base64 string out with '='s
            for (var i = 0; i < numberOfPaddingCharacters; i++)
                token += "=";

            return token;
        }

});

Answer 2

I guess that would be decodeuricomponent:
http://www.w3schools.com/jsref/jsref_decodeuricomponent.asp

To decode a UTF8-base64-encoded string in JavaScript:

var str2 = decodeURIComponent(escape(window.atob(b64)));
console.log(str2);

To encode a UTF8-JavaScript-string as such in JavaScript:

var str = "äöüÄÖÜçéèñ";
var b64 = window.btoa(unescape(encodeURIComponent(str)))
console.log(b64);

Seems UrlTokenDecode is a little bit more complicated.
The best method to be 100% sure is to call UrlTokenDecode on the server-side with AJAX, then return a simple base64-encoded string.

public static byte[] UrlTokenDecode (string input)
{
    if (input == null)
        throw new ArgumentNullException ("input");
    if (input.Length < 1)
        return new byte[0];
    byte[] bytes = Encoding.ASCII.GetBytes (input);
    int inputLength = input.Length - 1;
    int equalsCount = (int)(((char)bytes[inputLength]) - 0x30);
    char[] ret = new char[inputLength + equalsCount];
    int i = 0;
    for (; i < inputLength; i++) {
        switch ((char)bytes[i]) {
            case '-':
                ret[i] = '+';
                break;

            case '_':
                ret[i] = '/';
                break;

            default:
                ret[i] = (char)bytes[i];
                break;
        }
    }
    while (equalsCount > 0) {
        ret[i++] = '=';
        equalsCount--;
    }

    return Convert.FromBase64CharArray (ret, 0, ret.Length);
}

Source

Answer 3

This is possibly against the posting rules as its not an answer to the question but, I found this page whilst looking for the UrlTokenEncode method (not decode) so using the info here I made the following method which I hope helps someone else out:

function urlTokenEncode(str) {
    var b64 = btoa(encodeURIComponent(str).replace(/%([0-9A-F]{2})/g,
            function(match, t) {
                return String.fromCharCode('0x' + t);
            })),
        padChars = b64.match(/=/g);
    return b64.replace(/=/g, "") + (padChars == null ? 0 : padChars.length);
}

Tested and working with C# HttpServerUtility.UrlTokenEncode and HttpServerUtility.UrlTokenEncode

Answer 4

read this artical in MDN which describes the problem & solution:

https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding

function b64EncodeUnicode(str) {
    return btoa(encodeURIComponent(str).replace(/%([0-9A-F]{2})/g, function(match, p1) {
        return String.fromCharCode('0x' + p1);
    }));
}

b64EncodeUnicode('✓ à la mode'); // "4pyTIMOgIGxhIG1vZGU="