$apply() $digest()

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title></title>
</head>
<body ng-app="myApp">
    <div ng-controller="MessageController">
    Delayed Message: {{message}}
    </div>
    你应该使用$timeout service来代替setTimeout()，因为前者会帮你调用$apply()，让你不需要手动地调用它
    <script src="angular.min.js"></script>
    <script>   
    angular.module('myApp',[]).controller('MessageController', function($scope) {
    
      $scope.getMessage = function() {
           /*
        setTimeout(function() {
          $scope.message = 'Fetched after 3 seconds';
          console.log('message:'+$scope.message);
        }, 2000);
        */

        setTimeout(function() {  
          $scope.$apply(function() {  
            //wrapped this within $apply  
            $scope.message = 'Fetched after 3 seconds';   
            console.log('message:' + $scope.message);  
          });  
        }, 2000);  
      }
      
      $scope.getMessage();
    
    });
    </script>
</body>
</html>