enLOLcryption.

LOLcryption.js

String.prototype.enlolcrypt2 = function () {
    var cipher = "aeoiubcdfghjklmnpqrstvwxyz";
    return this.split("").map(function (T) {
        var c = /[A-Z]/.test(T), T = T.toLowerCase(), i = cipher.indexOf(T);
        if (/[^a-z]/.test(T)) { return T; }

        if (/[aeoiu]/.test(T)) {
          T = cipher[(i+2)%5];
        } else {
          T = cipher[(i+5)%21+5];
        }

        return c?T.toUpperCase():T;
    }).join("");
}

String.prototype.delolcrypt2 = function () {
    var cipher = "aeoiubcdfghjklmnpqrstvwxyz";
    return this.split("").map(function (T) {
        var c = /[A-Z]/.test(T), T = T.toLowerCase(), i = cipher.indexOf(T);
        if (/[^a-z]/.test(T)) { return T; }

        if (/[aeoiu]/.test(T)) {
          T = cipher[(i-2)%5];
        } else {
          T = cipher[(i-15)%21+5];
        }

        return c?T.toUpperCase():T;
    }).join("");
}

Minified:

String.prototype.lolcrypt2=function(){return this.split("").map(function(a){var b=/[A-Z]/.test(a),a=a.toLowerCase(),b="aeoiubcdfghjklmnpqrstvwxyz",c=b.indexOf(a);if(/[^a-z]/.test(a))return a;a=/[aeoiu]/.test(a)?b[(c+Math.floor(2.5))%5]:b[(c-5+Math.floor(10.5))%21+5];return b?a.toUpperCase():a}).join("")};