JavaScript Observer Pattern

Observer.js

/**
 * This module describes a Calculator. 
 * The calculator performs a single calculation of a 
 * given function, then sends the output to a list of
 * observers.
 */
var Calculator = (function() {
  
  
  /**
   * The function that will be used for calculation
   */
  var calculateFunction;
  
  
  /**
   * A list of observers
   */
  var observers = [];
  
 
  /**
   * Sends an object to all of the observers
   */
  function broadcastToObservers(obj) {
      for (var i = 0; i < observers.length; i++) {
          observers[i].observeFunc(obj);
      }
  }
  
  
  /**
   * Returns a function that can be instantiated
   */
  return function() {
    
    
    this.addObserver = function (o) {
        observers.push(o);
    }
    
    /**
     * Sets the function that will be used for calculation
     */
    this.setCalculateFunction = function(f) {
      calculateFunction = f;
    };
    
    
    /**
     * Performs a calculation for a given number of
     * iterations.
     */
    this.calculate = function(iterations) {
      var state = {};
      var data = {};
      for (var i = 0; i < iterations; i++) {
        calculateFunction(state);
        
        // quick and dirty clone of state
        data = JSON.parse(JSON.stringify(state));
        broadcastToObservers(data);
      }
    };
  }
})();


/**
 * This is a Sum module. It is meant to observe the
 * Calculator. Whenever the calculator performs a calculation,
 * it performs the designated observer function.
 */
var Sum = (function() {
    return function() {
        var sum = 0;
        
        /**
         * This is the function that will be called in Calculator.
         * It takes the data and adds it to the sum
         */
        this.observeFunc = function(data) {
            sum += data.x;
        }
        
        /**
         * Returns the current calculated sum
         */
        this.getSum = function() {
            return sum;
        }
    }
})();


/**
 * This is a Prduct module. It is meant to observe the
 * Calculator. Whenever the calculator performs a calculation,
 * it performs the designated observer function.
 */
var Product = (function() {
    return function() {
        var product = 1;
        
        /**
         * This is the function that will be called in Calculator.
         * It takes the data and adds it to the sum
         */
        this.observeFunc = function(data) {
            product *= data.x;
        }
        
        /**
         * Returns the current calculated sum
         */
        this.getProduct = function() {
            return product;
        }
    }
})();

/**
 * Create new instances of the Sum object, Product object, 
 * and the calculator object.
 */
var sumInstance = new Sum();
var productInstance = new Product();
var calculatorInstance = new Calculator();


/**
 * Add the sum object as an observer to the calculator and create the
 * calculate function. This function adds one the current state.
 */
calculatorInstance.addObserver(sumInstance);
calculatorInstance.addObserver(productInstance);
calculatorInstance.setCalculateFunction(function(state) {
    if (!state.x) {
        state.x = 1;
    }
    state.x++;
});


/**
 * Rund the calculations 5 times and output the sm to the console
 */
calculatorInstance.calculate(5);
console.log(sumInstance.getSum()); // 20
console.log(productInstance.getProduct()); // 720