角度控制器数组为空，即使我刚刚定义了它

Question

the following is a function in an angular controller. "alert (coffee.brand)", or any other part of the array, prints "undefined," which obviously it isn't. The weird part is, undefined prints the correct number of times in the for loop, so it knows the array is populated, it just can't seem to read the data. thoughts? Thanks in advance!

$scope.activate = function(id){


            $scope.coffees =
    [
    {'id': 1,
    'brand': 'Folgers',
    'name': 'Regular',
    'country': 'America',
    'reviews': [
            {'rating': 3,
            'comment': "gross",
            'reviewer': "James"
            }
    ]
    },
    {'id': 2,
    'brand': 'Starbucks',
    'name': 'Mocha',
    'country': 'America',
    'reviews': [
    {'rating': 7,
    'comment': 'insane!',
    'reviewer': 'Bob'
    },
    {'rating': 5,
    'comment': 'solid...',
    'reviewer': 'Joe'
    }
    ]
    }
    ];

            for (coffee in $scope.coffees){                       

                    alert (coffee.brand);
                    if (coffee.id == id){
                            $scope.currCoffee = coffee;
                            alert("here")
                            alert ($scope.currCoffee.id);
                    }
            }

    };

Answer 1

You are using the for in loop incorrectly. It does not iterate over elements in an array, but property names of an object. In your case, as you are using an implicitly numerically indexed array, it would be better to use a normal for loop, like so:

for (var i = 0; i < $scope.coffees.length; i++) {        
    var coffee = $scope.coffees[i];               
    alert (coffee.brand);
    if (coffee.id == id){
        $scope.currCoffee = coffee;
        alert("here")
        alert ($scope.currCoffee.id);
    }
}

See the documentation over at MDN for more information about the for in loop.

Answer 2

You should update the for loop to

for (var i = 0; i < $scope.coffees.length; i++) {

and retrieve values like

alert($scope.coffees[i].brand);

For reference - http://plnkr.co/edit/bmuJmJO94mEzGuB3uF0K?p=preview

Answer 3

coffee is key not the object itself, so go like $scope.coffees[coffee].

For more information

• for...in loop

  It iterates enumerable own and enumerable inherited properties.