if (!String.prototype.hasOwnProperty('rot13')) { String.prototype.rot13 = function (){ var rot = function(t, u, v){ return String.fromCharCode( ( ( t - u + v ) % ( v * 2 ) ) + u ); }, s = this, b = [], c, i = s.length, a = 'a'.charCodeAt(), z = a + 26, A = 'A'.charCodeAt(), Z = A + 26; while(i--) { c = s.charCodeAt( i ); if( c>=a && c<z ) { b[i] = rot( c, a, 13 ); } else if( c>=A && c<Z ) { b[i] = rot( c, A, 13 ); } else { b[i] = s.charAt( i ); } } return b.join( '' ); } }