AngularJS 双向绑定中字符串转数字及计算结果异常处理

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://cdn.static.runoob.com/libs/angular.js/1.4.6/angular.min.js"></script> 
</head>
<body>
<div ng-app="myApp">
<p ng-controller = "myContrl">结果为 <span ng-bind=""  ></span>
<input type="text" ng-model="first">{{first+second}}
  </p>
</div>
<script>
  var app = angular.module("myApp",[]);
  app.controller("myContrl",function($scope){
    $scope.first = 5;
    $scope.second =10;
  });
</script>
</body>
</html>

模板内隐式类型转换方案

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://cdn.static.runoob.com/libs/angular.js/1.4.6/angular.min.js"></script> 
</head>
<body>
<div ng-app="myApp">
<p ng-controller = "myContrl">结果为 <span ng-bind=""  ></span>
<input type="text" ng-model="first">{{first *1+second*1}}
  </p>
</div>
<script>
  var app = angular.module("myApp",[]);
  app.controller("myContrl",function($scope){
    $scope.first = 5;
    $scope.second =10;
  });
</script>
</body>
</html>

$watch监听与显式转换方案

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://cdn.static.runoob.com/libs/angular.js/1.4.6/angular.min.js"></script> 
</head>
<body>
<div ng-app="myApp">
<p ng-controller = "myContrl">结果为 <span ng-bind=""  ></span>
<input type="text" ng-model="first">{{total}}
  </p>
</div>
<script>
  var app = angular.module("myApp",[]);
  app.controller("myContrl",function($scope){
    $scope.first = 5;
    $scope.second =10;
    $scope.total = parseInt($scope.first)+parseInt($scope.second);
    $scope.$watch(function(){
    return $scope.first;
    },function(newValue,oldValue){
     if(newValue != oldValue){
      $scope.total = parseInt($scope.first)+parseInt($scope.second);
     }
    });
  });
</script>
</body>
</html>