JS Caffeine Script & Add property to every object in array & Counting power sets&Singleton Patter

Complete the function caffeineBuzz, which takes a non-zero integer as it's one argument.

If the integer is divisible by 3, return the string "Java".

If the integer is divisible by 3 and divisible by 4, return the string "Coffee"

If the integer is one of the above and is even, add "Script" to the end of the string.

Otherwise, return the string "mocha_missing!"

caffeineBuzz(1)   => "mocha_missing!"
caffeineBuzz(3)   => "Java"
caffeineBuzz(6)   => "JavaScript"
caffeineBuzz(12)  => "CoffeeScript"

//No.1
function caffeineBuzz(n){
  if (n % 12 === 0) return "CoffeeScript";
  if (n % 6 === 0) return "JavaScript";
  if (n % 3 === 0)  return "Java";
  return "mocha_missing!";
}

2.原型函数

function Dog(name, breed, sex, age){
    this.name  = name;
    this.breed = breed;
    this.sex   = sex;
    this.age   = age;

}
Dog.prototype.bark=function(){
  return 'Woof!';
}

3.Add property to every object in array

Your task is to add a new property usersAnswer to every object in the array questions. The value of usersAnswer should be set to null. The solution should work for array of any length.

For example:

var questions = [{
    question: "What's the currency of the USA?",
    choices: ["US dollar", "Ruble", "Horses", "Gold"],
    corAnswer: 0
}, {
    question: "Where was the American Declaration of Independence signed?",
    choices: ["Philadelphia", "At the bottom", "Frankie's Pub", "China"],
    corAnswer: 0
}];
After adding the property the result should be:

var questions = [{
    question: "What's the currency of the USA?",
    choices: ["US dollar", "Ruble", "Horses", "Gold"],
    corAnswer: 0,
    usersAnswer: null
}, {
    question: "Where was the American Declaration of Independence signed?",
    choices: ["Philadelphia", "At the bottom", "Frankie's pub", "China"],
    corAnswer: 0,
    usersAnswer: null
}];

//my answer:
for(var i=0;i<questions.length;i++){
    questions[i].usersAnswer=null;
    }

//NO.1
questions.forEach(function (i) {
        i.usersAnswer = null;
    });

4.Counting power sets

In this kata, you must create a function powers that takes an array, and returns the number of subsets possible to create from that list. In other words, counts the power sets.

For instance

powers([1,2,3]) => 8
...due to...

powerSet([1,2,3]) =>
[[],
 [1],
 [2],
 [3],
 [1,2],
 [2,3],
 [1,3],
 [1,2,3]]
Your function should be able to count sets up to the size of 500, so watch out; pretty big numbers occur there!

For comparison, my Haskell solution can compute the number of sets for an array of length 90 000 in less than a second, so be quick!

You should treat each array passed as a set of unique values for this kata.

//my
function powers(list) {
  // Program me!
  var pow=1;
  for(var i=0;i<list.length;i++)
  pow*=2;

  return pow;
}

//No.1
function powers(list) {
  return Math.pow( 2 ,list.length );
}

5.Singleton Pattern

In software engineering, the singleton pattern is a design pattern that restricts the instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system.

Create an Singleton pattern, so there is one object in system.

Example:

var obj1 = new Singleton();
var obj2 = new Singleton();
obj1 === obj2; // => true
obj1.test = 1;
obj2.test; // => 1

//my:错的
var Singleton = function(){
  // implement singleton Class

  Singleton.prototype.test=1;
};

//right:
var Singleton = function Singleton() {

  // Returns singleton in case it was already defined
  if (Singleton.prototype._singletonInstance) {
    return Singleton.prototype._singletonInstance;
  }

  // Otherwise defines singleton (to be returned next time around)
  Singleton.prototype._singletonInstance = this;

  // Defining properties
  this.test = 1;

};