it.js

//--INIT
h2b   = {a:['0'   ,'1'   ,'2'   ,'3'   ,'4'   ,'5'   ,'6'   ,'7'   ,'8'   ,'9'   ,'a'   ,'b'   ,'c'   ,'d'   ,'e'   ,'f'],
         b:['0000','0001','0010','0011','0100','0101','0110','0111','1000','1001','1010','1011','1100','1101','1110','1111']};
hexa  = '1c0111001f010100061a024b53535009181c';
hexb  = '686974207468652062756c6c277320657965';
hexc   = '';

for (var i = 0; i <= hexa.length-1; i++) {
 parta = parseInt(hexa.slice(i,i+1),16);
 partb = parseInt(hexb.slice(i,i+1),16);
 hexc += (parta^partb).toString(16);
};

console.log('\n\n');
console.log('output\n'+hexc+'\n\n');