ROT-13

rot13.js

String.prototype.map = function (fn) {
    var input = this;

    function step(acc, i, idx) {
        return acc + fn(i, idx, input);
    }

    return Array.prototype.reduce.call(this, step, "");
};

function rot13(c) {
    var read = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    var write = "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm";
    var p = read.indexOf(c);

    if (p > -1) {
        return write.charAt(p);
    }

    return c;
}

console.log("Lorem ipsum dolor sit amet, consectetur adipiscing elit. Duis elementum sagittis ultricies. Aenean convallis semper tortor. Sed nunc risus, pellentesque id ultricies ac, consequat et sem.".map(rot13));