https://mail.mozilla.org/pipermail/es-discuss/2011-October/017130.html

grawlix.js

var GRAWLIX = "@#$%&*";
String.prototype.grawlix = function () {
    return this.split(" ").map(function (word) {
        var dictionary = {};
        var previous;
        return Array.prototype.map.call(word, function (char) {
            if (!/\w/.test(char))
                return char;
            var code = char.charCodeAt();
            if (!dictionary[code]) {
                dictionary[code] = GRAWLIX[code % GRAWLIX.length];
                if (previous == dictionary[code])
                    dictionary[code] = GRAWLIX[(code + 1) % GRAWLIX.length];
                previous = dictionary[code];
            }
            return dictionary[code];
        }).join("");
    }).join(" ");
};

console.log("fuck".grawlix());
console.log("ass".grawlix());
console.log("poo darn!!".grawlix());