change_machine.js

'use strict';

function ChangeMachine() {

  var coins = {
    '75p'  : 75,
    '15p'  : 15,
    '3p'   : 3,
    '1p'   : 1,
    '1/2p' : 0.5,
    '1/4p' : 0.25
  }

  var convertPoundsToPennies = function(pounds) {
    return pounds * 100;
  };

  var inputVerification = function(price, payed) {
    if (typeof price !== 'number' || typeof payed !== 'number') {
      throw 'please enter a number';
    } else if (price > payed) {
      throw 'not enough payed';
    } else if (price * 100 < 0.25) {
      throw 'enter a higher price';
    } else if (price == payed) {
      throw 'no change needed';
    } else if (price <= 0 || payed <= 0) {
      throw 'This is not a correct price';
    }
    return false;
  };

  this.returnChange = function(pricePounds, payedPounds) {
    var error;
    var changeObject = [];
    var totalChange;
    var price        = convertPoundsToPennies(pricePounds);
    var payed        = convertPoundsToPennies(payedPounds);
    try {
      error = inputVerification(price, payed);
      if (!error) {
        totalChange = payed - price;
        var coinNames;
        for (coinNames in coins) {
          if (coins.hasOwnProperty(coinNames)) {
            var coinValue  = coins[coinNames];
            var coinsCount = parseInt((totalChange / coinValue), 10);
            if (coinsCount >= 1) {
              changeObject.push({
                name : coinNames,
                n    : coinsCount
              });
            }

            //how much change is left over
            totalChange = totalChange % coinValue;

          }
        }
        return changeObject;
      }
    }catch (error) {
      console.log(error);
      return false;
    }
  };

}

var pricePounds = 1;
var payedPounds = 2;

var machine = new ChangeMachine();

var change = machine.returnChange(pricePounds, payedPounds);
console.log(change);