+Util.prototype.rot13 = function(chaine)
+{
+ var ACode = 'A'.charCodeAt(0)
+ var aCode = 'a'.charCodeAt(0)
+ var MCode = 'M'.charCodeAt(0)
+ var mCode = 'm'.charCodeAt(0)
+ var ZCode = 'Z'.charCodeAt(0)
+ var zCode = 'z'.charCodeAt(0)
+
+ var f = function(ch, pos) {
+ if (pos == ch.length)
+ return ""
+
+ var c = ch.charCodeAt(pos);
+ return String.fromCharCode(
+ c +
+ (c >= ACode && c <= MCode || c >= aCode && c <= mCode ? 13 :
+ (c > MCode && c <= ZCode || c > mCode && c <= zCode ? -13 : 0))
+ ) + f(ch, pos + 1)
+ }
+ return f(chaine, 0)
+}
+