Gist from mistakes.io

index.js

function decode(str) {
var id = str.split('');
var pts = [];
while (id.length) { pts.push([id.shift(), id.shift()].join('')) }
return pts.map(function(p) {
  return String.fromCharCode(parseInt(p, 16));
}).join('');
}

function encode(str) {
  var chars = str.split('');
  return chars.map(function(c) {
    return c.charCodeAt(0).toString(16);
  }).join('');
}

encode('TILE');
decode(encode('TILE'));

decode('45737269');
decode('47503130')
decode('5f4d544e')
decode('42654c6e')