Vfrdtyky

I'm thinking about using the encode/decode technique here (Encoding to base 36/decoding from base 36 is simple in Ruby)

how to implement a short url like urls in twitter?

Idea being to track user referrals, invite URLs. I can use Rails to decode, but it there a way to encode with Javascript or jQuery?

The toString method on Number has an optional argument of radix:

(128482).toString(36);

128482..toString(36);

128482 .toString(36);

var num = 128482; num.toString(36);

Note this doesn't work, because numbers expect decimal digits after a period, not letters:

128482.toString(36);  // Syntax error

Also, you can decode with JS as well:

parseInt("2r4y", 36);

For anyone looking for how to encode a string in base36 (since this question, How do i convert string to base36 in javascript , is redirected here) -

Here's what I came up with.

/* encode / decode strings to / from base36 



   based on: http://snipplr.com/view/12653/

*/



var base36 = {

    encode: function (str) {

        return Array.prototype.map.call(str, function (c) {

            return c.charCodeAt(0).toString(36);

        }).join("");

    },

    decode: function (str) {

        //assumes one character base36 strings have been zero padded by encodeAscii

        var chunked = ;

        for (var i = 0; i < str.length; i = i + 2) {

            chunked[i] = String.fromCharCode(parseInt(str[i] + str[i + 1], 36));

        }

        return chunked.join("");

    },

    encodeAscii: function (str) {

        return Array.prototype.map.call(str, function (c) {

            var b36 = base36.encode(c, "");

            if (b36.length === 1) {

                b36 = "0" + b36;

            }

            return b36;

        }).join("")

    },

    decodeAscii: function (str) {

        //ignores special characters/seperators if they're included

        return str.replace(/[a-z0-9]{2}/gi, function (s) {

            return base36.decode(s);

        })

    }

};



var foo = "a-Az-Z 0-9 !@#$%^&*()-_=+[{]};:',<.>/?`~";

var bar = base36.encodeAscii(foo);



console.log(foo);

console.log(base36.decode(bar));



console.log('');



var bar = "==/" + bar + "\==";

console.log(bar)

console.log(base36.decodeAscii(bar));





//doesn't work

console.log('');

var myString = "some string";

var myNum = parseInt(myString, 36);

console.log(myNum.toString(36))



myString = "FooBarW000t";

myNum = parseInt(myString, 36);

console.log(myNum.toString(36))



myString = "aAzZ09!@#$%^&*()-_=+[{]};:',<.>/?`~";

myNum = parseInt(myString, 36);

console.log(myNum.toString(36))



/* 

Outputs:



a-Az-Z 0-9 !@#$%^&*()-_=+[{]};:',<.>/?`~

a-Az-Z 0-9 !@#$%^&*()-_=+[{]};:',<.>/?`~



==/2p191t3e192i0w1c191l0w0x1s0z10112m12161415192n1p172j3f2l3h1n1m13181o1a1q1b1r2o3i==

==/a-Az-Z 0-9 !@#$%^&*()-_=+[{]};:',<.>/?`~==



some

foobarw000w

aazz09

*/

For anyone looking to decode @imjosh's answer in python (say if you've encoded client-side and need to decode server-side), this is what I used. I would have left as a comment in @imjosh's answer but comments don't format very well.

def decodeBase36(str):

  decoded_str = ""

  for i in range(0, len(str), 2):

    char = chr(int(str[i:i+2], 36))

    decoded_str += char

  return decoded_str

and a not-as-elegant Objective-C version:

+ (NSString *)b36DecodeString:(NSString *)b36String

{

    NSMutableString *decodedString = [NSMutableString stringWithFormat:@""];

    for (int i = 0; i < [b36String length]; i+=2) {

        NSString *b36Char = [b36String substringWithRange:NSMakeRange(i, 2)];

        int asciiCode = 0;

        for (int j = 0; j < 2; j++) {

            int v = [b36Char characterAtIndex:j];

            asciiCode += ((v < 65) ? (v - 48) : (v - 97 + 10)) * (int)pow(36, 1 - j);

        }

        [decodedString appendString:[NSString stringWithFormat:@"%c", asciiCode]];

    }

    return decodedString;

}