Question

我有一个这样的对象：

var animals_data = {
category : [
    {
        class : "Reptiles",
        animals : [
            {
                image1 : "some image",
                image2 : "some image 2",
                name : "Snake",
                description : "some description"
            },
            {
                image1 : "another image",
                image2 : "another image 2",
                name : "Crocodilia",
                description : "another description"
            },
        ]
    },
    {
        class : "Mammals",
        animals : [
            {
                image1 : "more image",
                image2 : "more image 2",
                name : "Cat",
                description : "more description"
            },
            {
                image1 : "image",
                image2 : "image 2",
                name : "Dog",
                description : "long description"
            }
        ]
    },
    {
        class : "Birds",
        animals : [
            {
                image1 : "bird image",
                image2 : "bird image 2",
                name : "American flamingo",
                description : "bird description"
            },
            {
                image1 : "another bird image",
                image2 : "another bird image 2",
                name : "Atlantic puffin",
                description : "another bird description"
            },
        ]
    }

]};

我想获取firstIndex的值并将它们放在不同的数组中。但是，我很难做到这一点。我做的代码是：

for (var i = 0; i < animals_data.category.length; i++) {
var currentIteration = animals_data.category[i];    
var currentClass = currentIteration.class;

animals_array.push(currentClass);
};

当我运行代码时，错误说明：无法读取未定义的属性“firstIndex”。谢谢你的帮助。

编辑：包含我正在使用的实际对象。我省略了一些部分，但基本上，这就是要点。我想要放在一个新数组中的值是“class”属性中的值。

Answer 1

解决了它。谢谢Xotic750指出这个错误。我的问题是：

我用的时候：

for (var i = 0; i < obj.firstKey.length; i++); {
var currentIteration = obj.firstKey[i];
var currentIndex = currentIteration.firstIndex;

new_array.push(currentIndex);
};

阵列加倍（即每个阵列加两个）。

然而当我用

替换它时

new_array.push(obj.firstKey[i].firstIndex;

它运行正常。我可以知道为什么会有这样的差异吗？谢谢。

Answer 2

必须清理提供的数据结构和任何列表结构那些成员只需要从一种类型/形式转变为另一种类型/形式，由map最佳处理。

var
    animalData = {
        categories: [{

            class   : "Reptiles",
            animals : [{

                image1 : "some image",
                image2 : "some image 2",
                name : "Snake",
                description : "some description"
            }, {
                image1 : "another image",
                image2 : "another image 2",
                name : "Crocodilia",
                description : "another description"
            }]

        }, {
            class   : "Mammals",
            animals : [{

                image1 : "more image",
                image2 : "more image 2",
                name : "Cat",
                description : "more description"
            }, {
                image1 : "image",
                image2 : "image 2",
                name : "Dog",
                description : "long description"
            }]

        }, {
            class   : "Birds",
            animals : [{

                image1 : "bird image",
                image2 : "bird image 2",
                name : "American flamingo",
                description : "bird description"
            }, {
                image1 : "another bird image",
                image2 : "another bird image 2",
                name : "Atlantic puffin",
                description : "another bird description"
            }]
        }]
    },

    animalClassNameList = animalData.categories.map(function (category) {
        return category.class;
    });


console.log("animalData : ", animalData);
console.log("animalClassNameList : ", animalClassNameList);

将数组内对象的值传递给另一个数组

2 个答案: