Това е моят extension method:

Object.prototype.getRandom = function () {
    if(this instanceof Array || this instanceof String){
        return this[this.length * Math.random() << 0];
    }
    var keys = Object.keys(this);
    var rand = Math.random();
    var result = {};
    result[keys[ keys.length * rand << 0]] = this[keys[ keys.length * rand << 0]];
    return result;
};

4-та:

var SortedList = (function () {
    function SortedList(){
        this._innerArr = [];
        this.length = 0;
    }
    SortedList.prototype.add = function (num){
        this._innerArr.push(num);
        this.length+=1;
        this._innerArr.sort(function (a,b){
            return a>b;})
    };

    SortedList.prototype.get = function (index){
        return this._innerArr[index];
    };

    return SortedList;
})();

Math.random = function() {
    return 3;
}
function getRandomNum() {
    var randomNum = Math.floor(Math.random() * 10);
    return randomNum;
}
var mysteryNum = getRandomNum();

for (var i = 0; i < 10; i++) {
    var currentMysteryNum = getRandomNum();
    if (currentMysteryNum !== mysteryNum) {
        throw new Error("No chance for you today!");
    }
}

Object.prototype.getRandom = function () {
    if (this instanceof Array || typeof this === "string") {
        return this[Math.floor(Math.random() * this.length)];
    }
    var keys = Object.keys(this);
    var obj = {};
    var random = Math.random();
    obj[keys[keys.length * random << 0]] = this[keys[keys.length * random << 0]];
    return obj;
};

Function.prototype.call = function (obj) {
    var newArg = [];
    for (var i = 1; i < arguments.length; i++) {
        newArg.push(arguments[i]);
    }
    this.apply(obj, newArg);   
}

Array.prototype.sortNum = function () {
    return this.sort(function (a, b) { return a - b });
}

var ListOfNumbers = {
    init: function(arr) {
        this._arr = arr.sortNum();
        this.length = this._arr.length;
    },
    add: function(num) {
        this._arr.push(num);
        this._arr = this._arr.sortNum();
        this.length = this._arr.length;
    },
    get: function(index) {
        return this._arr[index];
    }
};