利用AngularJs实现价格计算器，总价满100免运费。(熟悉$watch的使用)
代码：
<!DOCTYPE html>
<html lang="en" ng-app="myApp">
<head>
<meta charset="UTF-8">
<title>价格计算器</title>
<link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/4.0.0-alpha.2/css/bootstrap.min.css">
</head>
<body>
<div class="container" ng-controller="MyControl">
<h2>价格计算器</h2>
单价：<input type="text" class="form-control" ng-model="iphone.price">
数量：<input type="text" class="form-control" ng-model="iphone.num">
<hr>
<p>总价：{{ sum() | currency:'￥'}}</p>
<p>运费：{{ iphone.yf | currency:'￥'}}</p>
<p>合计：{{ sum() + iphone.yf | currency:'￥'}}</p>
</div>
<script src="http://apps.bdimg.com/libs/angular.js/1.4.6/angular.min.js"></script>
<script>
var myAng = angular.module('myApp',[]);
myAng.controller('MyControl',function($scope){
$scope.iphone = {
price:10,
num:1,
yf:10
}
$scope.sum = function(){
return $scope.iphone.price*$scope.iphone.num
}
// $watch监控对象为属性时，不加$scope
$scope.$watch('iphone.num',function(newvalue,oldvalue){
console.log('新值：'+ newvalue +'；旧值：'+ oldvalue)
})
// $watch监控对象为方法时，加$scope
$scope.$watch($scope.sum,function(newvalue,oldvalue){
return $scope.iphone.yf = newvalue >= 100 ? 0 : 10;
})
})
</script>
</body>
</html>
