function cipherRot13(str) {
str = str.toUpperCase();
return str.replace(/[A-Z]/g, rot13);
function rot13(correspondance) {
const charCode = correspondance.charCodeAt();
//A = 65, Z = 90
return String.fromCharCode(
((charCode + 13) <= 90) ? charCode + 13
: (charCode + 13) % 90 + 64
);
}
}