JSFiddle - React, Tailwind, and code Playground

HTML

Encoded: <br /><textarea>0,0,60,5d,17,1f,5b,66,5a,6c,64,5c,65,6b,25,5e,5c,6b,3c,63,5c,64,5c,65,6b,6a,39,70,4b,58,5e,45,58,64,5c,1f,1e,59,66,5b,70,1e,20,52,27,54,20,72,4,0,0,0,60,5d,69,58,64,5c,69,1f,20,32,4,0,0,74,17,5c,63,6a,5c,17,72,4,0,0,0,5b,66,5a,6c,64,5c,65,6b,25,6e,69,60,6b,5c,1f,19,33,60,5d,69,58,64,5c,17,6a,69,5a,34,1e,5f,6b,6b,67,31,26,26,69,66,6b,58,6b,5c,6b,5f,5c,6a,67,60,65,25,5a,66,64,31,2f,27,27,27,26,63,5f,5f,68,65,5a,5a,68,6a,36,5d,6b,59,5f,62,67,64,5a,66,69,6b,34,2c,28,2f,2d,2e,2c,28,1e,17,6e,60,5b,6b,5f,34,1e,28,27,27,1e,17,5f,5c,60,5e,5f,6b,34,1e,28,27,27,1e,17,6a,6b,70,63,5c,34,1e,6e,60,5b,6b,5f,31,28,27,27,67,6f,32,5f,5c,60,5e,5f,6b,31,28,27,27,67,6f,32,67,66,6a,60,6b,60,66,65,31,58,59,6a,66,63,6c,6b,5c,32,63,5c,5d,6b,31,24,28,27,27,27,27,67,6f,32,6b,66,67,31,27,32,1e,35,33,26,60,5d,69,58,64,5c,35,19,20,32,4,0,0,74,4,0,0,5d,6c,65,5a,6b,60,66,65,17,60,5d,69,58,64,5c,69,1f,20,72,4,0,0,0,6d,58,69,17,5d,17,34,17,5b,66,5a,6c,64,5c,65,6b,25,5a,69,5c,58,6b,5c,3c,63,5c,64,5c,65,6b,1f,1e,60,5d,69,58,64,5c,1e,20,32,5d,25,6a,5c,6b,38,6b,6b,69,60,59,6c,6b,5c,1f,1e,6a,69,5a,1e,23,1e,5f,6b,6b,67,31,26,26,69,66,6b,58,6b,5c,6b,5f,5c,6a,67,60,65,25,5a,66,64,31,2f,27,27,27,26,63,5f,5f,68,65,5a,5a,68,6a,36,5d,6b,59,5f,62,67,64,5a,66,69,6b,34,2c,28,2f,2d,2e,2c,28,1e,20,32,5d,25,6a,6b,70,63,5c,25,63,5c,5d,6b,34,1e,24,28,27,27,27,27,67,6f,1e,32,5d,25,6a,6b,70,63,5c,25,6b,66,67,34,1e,27,1e,32,5d,25,6a,6b,70,63,5c,25,67,66,6a,60,6b,60,66,65,34,1e,58,59,6a,66,63,6c,6b,5c,1e,32,5d,25,6a,6b,70,63,5c,25,6b,66,67,34,1e,27,1e,32,5d,25,6a,5c,6b,38,6b,6b,69,60,59,6c,6b,5c,1f,1e,6e,60,5b,6b,5f,1e,23,1e,28,27,27,1e,20,32,5d,25,6a,5c,6b,38,6b,6b,69,60,59,6c,6b,5c,1f,1e,5f,5c,60,5e,5f,6b,1e,23,1e,28,27,27,1e,20,32,4,0,0,0,5b,66,5a,6c,64,5c,65,6b,25,5e,5c,6b,3c,63,5c,64,5c,65,6b,6a,39,70,4b,58,5e,45,58,64,5c,1f,1e,59,66,5b,70,1e,20,52,27,54,25,58,67,67,5c,65,5b,3a,5f,60,63,5b,1f,5d,20,32,4,0,0,74</textarea>
<hr />
base:      <input title="base/radix: 2 to 36" 
                 ...

CSS

html, body { height:100%; }
textarea   { width:99%; height:35%; }
input      { width:2em; text-align:center; 
             border:1px solid #fedfdf; background:#f7f7f7; }

JavaScript

var dencode=function(opt){
    var L = document,    enc = [],    dec = [],
        i = L.getElementsByTagName('input'),
      rad = Number(i[0].value) || 10,
      sep = i[1].value || ',',
      ofs = Number(i[2].value) || 0,
      txt = L.getElementsByTagName('textarea');

    if (opt === 'enc') {                        // encode
        dec = txt[1].value.split('');
        for (i = 0, L = dec.length; i < L; i++) {
            enc.push( (dec[i].charCodeAt(0)-ofs).toString(rad) );
        }
        txt[0].value = enc.join(sep);
    } else {                                    // decode (default)
        enc = txt[0].value.replace(/[\r\n]/gi,'').split(sep);
        for (i = 0, L = enc.length; i < L; i++) {
            dec.push(  String.fromCharCode( parseInt(enc[i],rad)+ofs )  );
        }
        txt[1].value = dec.join('');
    }
};