js-best-practices

2-balanceManager.js

//Exercise 2 Separation of Concerns 1 
//Separation of Concerns Part 1

/*take the 4 methods and any variables that relate to
  balance management and move them to balanceManager.js. Then, back in
  vendingMachine.js, change the method of calling those functions from this
  to our new balanceManager
*/

var balance = 0;

module.exports = {

  canAfford: function(amount){
    if(!this.isValidAmount(amount)){
      errorMessage = "Invalid Input";
    }
    if(errorMessage){
      throw new Error(errorMessage);
    }
    return amount <= balance;
  },

  decreaseBalance: function(amount){
    // This method decreases the balance of the vending machine. If the balance amount is not 
    // enough to cover the purchase, the method throws an error. 
    var errorMessage;
    if(!this.canAfford(amount)){
        errorMessage = 'Insufficient balance';
    }
    if(errorMessage){
        throw new Error(errorMessage);
    }
    balance -= amount;
  },
  
  getBalance: function(){ 
    return balance;
  },
  
  increaseBalance: function(amount){
    balance += amount;
  },
  
};

3-changeHandler.js

//Exercise 3  Separation of Concerns Part 2

/*We have already separated out all of the balance related methods, now we
will look at the change related ones. Take the method that relates to
handling change and move it into changeHandler.js
*/
module.exports = {
    getAmount: function(coinType) {
        // COINS:
        // [p]enny
        // [n]ickel
        // [d]ime
        // [q]uarter
        switch(coinType){
          case 'p': return 1;
          case 'n': return 5;
          case 'd': return 10;
          case 'q': return 25;
          default: throw new Error('Unrecognized coin ' + coinType);
        }
      }
};

4-productInventory.js

//Exercise 4 Separation of Concerns 3

/*Take the two methods that relate to products and move them into
  productInventory.js
 */
var products = [
    {
        name: 'Skittles',
        price: 85,
        id: 'A1'
    }
];

module.exports = {
    getProducts: function () {
        return products;
    },

    getProduct: function (productId) {
        var product = products.find(function (p) { return p.id === productId; });
        return product;
    }
};

5-changeHandler1.js

//Exercise 5 Getting Rid of Switch Statements

/*you should refactor the getAmount() method in
  changeHandler.js to completely remove the switch method while retaining
  its functionality. It doesn't matter what alternative you choose, but the
  method should not use a switch statement in any way
*/
// COINS:
// [p]enny
// [n]ickel
// [d]ime
// [q]uarter

var coins = {
    p: 1,
    n: 5,
    d: 10,
    q: 25
  };
  
  module.exports = {
    
    getAmount: function(coinType) {
        if (coins.hasOwnProperty(coinType)) {
          return coins[coinType];
        }
        throw new Error('Unrecognized coin ' + coinType);
      }
  };

6-changeHandler2.js

//Exercise 6

/*The tests in this exercise are provided, but they will drive the design of
  the function you will implement, convertToChange(). convertToChange()
  should take in a single integer number in cents (e.g. $0.89 = 89) and
  return an array of the coins that would add up to this number. Keep in
  mind that the array of coins should be in the highest order in terms of
  coin value. For example, if 26 is the parameter, you should return 1 penny
  and 1 quarter in the array, even though you could technically return
  several other combinations of coins (e.g. 2 dimes, 1 nickel, 1 penny)
*/
// COINS:
// [p]enny
// [n]ickel
// [d]ime
// [q]uarter

var coins = {
    p: 1,
    n: 5,
    d: 10,
    q: 25
  };
  
  var coinsByAmount = ['q', 'd', 'n', 'p'];

  module.exports = {
      convertToChange: function(amount) {
        var change = [];
        for(var i in coinsByAmount){
          var coinType = coinsByAmount[i];
          var coinValue = coins[coinType];
    
          while(amount >= coinValue){
            change.push(coinType);
            amount -= coinValue;
          }
        }
        return change;
      }
    };

7-balanceManager1.js

//Exercise 7 Fix Your Teammates' Mistakes

var balance = 0;

    module.exports = {
      increaseBalance: function(amount){
        balance += amount;
      },
      getBalance: function(){
        return balance;
      },
      canAfford: function(amount){
        var errorMessage;
        if(!this.isValidAmount(amount)){
            errorMessage = 'Invalid Input';
        }
        if(errorMessage){
            throw new Error(errorMessage);
        }
        return amount <= balance;
      },
      decreaseBalance: function(amount){
        if(!this.canAfford(amount)){
          var errorMessage = 'Insufficient balance';
        }
        if(errorMessage){
          throw new Error(errorMessage);
        }
        balance -= amount;
      },
      isValidAmount: function(amount){
        if(!amount){
          return false;
        } else {
          return true;
        }
      }
    };