SOURCE

(function(angular){
  angular.module('invoice1',[])
  .controller("InvoiceController",function InvoiceController(){
    this.qty = 1;
    this.cost = 2;
    this.inCurr = "美元";
    this.currencies = ["美元","欧元","人民币"];
    this.usdToForeignRates = {
      美元:1,
      欧元:0.74,
      人民币: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!');
    };
  });
})(window.angular)

<div ng-app='invoice1' ng-controller="InvoiceController as invoice">
  <b>发票</b>
  <div>
    数量:<input  type="number" ng-model="invoice.qty" required></input>
  </div>
 <div>
    单价:<input  type="number" ng-model="invoice.cost" required></input>
   <select ng-model="invoice.inCurr">
    <option ng-repeat="c in invoice.currencies">{{c}}</option>
  </select>
  </div>
  <div>
    <b>总价：</b>
    <span ng-repeat="c in invoice.currencies">
      {{invoice.total(c)|currency:c}}
    </span><br />
    <button ng-click="invoice.pay()">支付</button>
  </div>
</div>