Caesar cipher

https://en.wikipedia.org/wiki/Caesar_cipher

by Harm Zeinstra

JavaScript

var encrypt = function(s, change) {
  return s.replace(/[a-zA-Z]/g, function(c) {
    return String.fromCharCode((c <= "Z" ? 90 : 122) >= (c = c.charCodeAt(0) + (13 - change)) ? c : c - 26);
  });
}

var decrypt = function(s, change) {
  return s.replace(/[a-zA-Z]/g, function(c) {
    return String.fromCharCode((c <= "Z" ? 90 : 122) >= (c = c.charCodeAt(0) + (13 + change)) ? c : c - 26);
  });
}


var change = 0;
var s = 'Bvmfzmn rzb, yzpm ydxco yjzi diydzi hjbzgdef';
var e = encrypt(s, change);
var s2 = decrypt(e, change);

for(var i =-13; i<13; i++) console.log(decrypt(s, i))

console.log(s);
console.log('~~~~~~');
console.log(e);
console.log(s2);
console.log('~~~~~~');
change = 9;
e = encrypt(s, change);
s2 = decrypt(e, change);
console.log(e);
console.log(s2);
console.log('~~~~~~');
change = 3;
e = encrypt(s, change);
s2 = decrypt(e, change);
console.log(e);
console.log(s2);


console.log('------------------');