我正在使用MERN堆栈构建一个非常简单的虚构运动鞋应用程序。我不会称自己为新手，但我也不是专家。我能够很好地创建后端并生成一个json rest api。我的问题出在前端。我只是想从一个对象中console.log一个属性。
例如，我有一条路线，它可以得到一组运动鞋对象。在每个对象中，它都包含运动鞋型号、配色、运动鞋发布年份等信息，这里是对象的预览。
{
"_id": "5c5dff42489e28576c28cd9e",
"model": "Air Jordan 11",
"colorway": "Win Like 82",
"year": 1997,
"text": "Cool kicks",
"mainimage": "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664062/xjwkpbqwl1pmawpocygx.jpg",
"subimage_1": "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664062/y8h1biytup4rgxqrm2qe.jpg",
"subimage_2": "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664063/wrwska4tnog4vselcwp7.jpg",
"subimage_3": "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664063/h9dyki3gdgfjcccchhia.jpg",
"subimage_4": "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664064/qwrsabomnsqk7pjyx5ss.jpg",
"user": "5c4b4635c9de365620cd797b",
"likes": [],
"comments": [],
"date": "2019-02-08T22:14:26.127Z",
"__v": 0
}
我使用destructuring从我的应用程序(Redux)状态获取运动鞋数据：const { sneakers } = this.props.sneaker;
当我尝试使用console.log(sneakers)对对象数组进行console.log操作时，它会按预期工作，结果如下：
(3) [{…}, {…}, {…}]
0:
colorway: "Win Like 82"
comments: []
date: "2019-02-08T22:14:26.127Z"
likes: []
mainimage: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664062/xjwkpbqwl1pmawpocygx.jpg"
model: "Air Jordan 11"
subimage_1: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664062/y8h1biytup4rgxqrm2qe.jpg"
subimage_2: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664063/wrwska4tnog4vselcwp7.jpg"
subimage_3: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664063/h9dyki3gdgfjcccchhia.jpg"
subimage_4: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549664064/qwrsabomnsqk7pjyx5ss.jpg"
text: "Cool kicks"
user: "5c4b4635c9de365620cd797b"
year: 1997
__v: 0
_id: "5c5dff42489e28576c28cd9e"
__proto__: Object
1:
colorway: "taxi"
comments: []
date: "2019-02-08T19:20:59.467Z"
likes: []
mainimage: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653655/gag2aktdhyfru5s5dnni.jpg"
model: "Air Jordan 12"
subimage_1: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653656/wcg9jmo84cl8mhxb2iwl.jpg"
subimage_2: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653656/mxistpujhh0xikzqwcu0.jpg"
subimage_3: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653657/dcp1y2jrqz2nkgyhuwfr.jpg"
subimage_4: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653657/dyee9uzb7aj1dp46rlnj.jpg"
text: "the holy grails"
user: "5c4b4635c9de365620cd797b"
year: 1997
__v: 0
_id: "5c5dd69beaef7140e0d2926d"
__proto__: Object
2:
colorway: "Obsidian"
comments: []
date: "2019-02-03T23:01:21.937Z"
likes: []
mainimage: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549234878/yzdoot1cf3jnbq31ndkg.jpg"
model: "Air Jordan 12"
subimage_1: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549234879/jbjw8hngvieyvnizfb8b.jpg"
subimage_2: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549234880/qu1gguxpfp2mapd5ivo2.jpg"
subimage_3: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549234880/gcntdjlznjjbxifsmufl.jpg"
subimage_4: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549234881/ck9emeurmaqleizaqe1e.jpg"
text: "Awesome kicks"
user: "5c4b4553c9de365620cd797a"
year: 1997
__v: 0
_id: "5c5772c10ffd0f2e789999b2"
__proto__: Object
length: 3
__proto__: Array(0)
例如，如果我想说我使用的第二款运动鞋：
console.log(sneakers[1])
我得到了我所期望的：
{_id: "5c5dd69beaef7140e0d2926d", model: "Air Jordan 12", colorway: "taxi", year: 1997, text: "the holy grails", …}
colorway: "taxi"
comments: []
date: "2019-02-08T19:20:59.467Z"
likes: []
mainimage: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653655/gag2aktdhyfru5s5dnni.jpg"
model: "Air Jordan 12"
subimage_1: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653656/wcg9jmo84cl8mhxb2iwl.jpg"
subimage_2: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653656/mxistpujhh0xikzqwcu0.jpg"
subimage_3: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653657/dcp1y2jrqz2nkgyhuwfr.jpg"
subimage_4: "http://res.cloudinary.com/dwgjvssdt/image/upload/v1549653657/dyee9uzb7aj1dp46rlnj.jpg"
text: "the holy grails"
user: "5c4b4635c9de365620cd797b"
year: 1997
__v: 0
_id: "5c5dd69beaef7140e0d2926d"
__proto__: Object
然而，当我试图从一款运动鞋中获得属性时，比如说我使用的第二款运动鞋的配色：
console.log(sneakers[1].colorway)
我遇到了这个错误TypeError: Cannot read property 'colorway' of undefined。
我有点难以理解为什么。我想，如果我想的话，我可以从一个运动鞋中记录数据，我应该能够从那个运动鞋中只记录一个属性。很明显，有些事情我做得不太好，但我不知道是什么。
很可能，数据对象打印是为了方便浏览器级别，但实际上还没有准备好进行属性访问。为了避免这个问题，我成功地使用了这个模式：
const SomeComponent = ({sneakers}) => {
return (
<div>
{
sneakers && sneakers.map(sneaker => {
return (
<div>{sneaker.colorway}</div>
)
})
}
</div>
)
}
export default SomeComponent;