sample angularjs invoice with currency

<!DOCTYPE html>
<html lang="en-US">
    <!--
        Belajar Angular JS dengan praktek 3
        invoice dan currency
        tema: filter
        Yoesoff / Yusuf
        blog : undebugable.wordpress.com
        penjelasan :  Belajar praktek angularJS
     -->
    <head>
        <!-- Load Angular -->
        <script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js"></script>
    </head>

    <body>
        <div ng-app="invoice1" ng-controller="InvoiceController as invoice">
              <b>Invoice:</b>

              <div>
                Quantity: <input type="number" min="0" ng-model="invoice.qty" required >
              </div>

              <div>
                Costs: <input type="number" min="0" ng-model="invoice.cost" required >
                <select ng-model="invoice.inCurr">
                  <option ng-repeat="c in invoice.currencies">{{c}}</option>
                </select>
              </div>

              <div>
                <b>Total:</b>
                <span ng-repeat="c in invoice.currencies">
                  {{invoice.total(c) | currency:c}}
                </span>
                <button class="btn" ng-click="invoice.pay()">Pay</button>
              </div>
        </div>
    </body>

    <script>
    var app = angular.module('invoice1', []);
    app.controller('InvoiceController', function() {
          this.qty = 1;
          this.cost = 2;
          this.inCurr = 'EUR';
          this.currencies = ['USD', 'EUR', 'CNY'];

          this.usdToForeignRates = {
            USD: 1,
            EUR: 0.74,
            CNY: 6.09
          };

          this.total = function total(outCurr) {
            return this.convertCurrency(this.qty * this.cost, this.inCurr, outCurr);
          };
          this.convertCurrency = function convertCurrency(amount, inCurr, outCurr) {
            return amount * this.usdToForeignRates[outCurr] / this.usdToForeignRates[inCurr];
          };
          this.pay = function pay() {
            window.alert("Thanks!");
          };
    });

    </script>

</html>