如何使用 map 函数，以便将索引作为属性添加到新构造的对象中？

Question

我有一个索引数组：例如selected = [2, 6, 10] ()。我还有一组名为 photos 的照片对象。我只想跟踪选定的照片，所以我这样做:

const selectedPhotos = selectedArray.map((i) => photos[i]);

这给了我结果：

Array [
  Object {
    "albumId": "someId1",
    "creationTime": "sometime",
    "duration": 0,
    "filename": "name1.jpg",
    "id": "someId1",
    "uri": "someIUri1",
  },
  Object {
    "albumId": "someId2",
    "creationTime": "sometime",
    "duration": 0,
    "filename": "name2.jpg",
    "id": "id2",
    "uri": "uri2",
  },
  Object {
    "albumId": "someId3",
    "creationTime": "sometime",
    "filename": "filename3.jpg",
    "uri": "uri3",
  },
 ]

这很好，但是我还想跟踪所选索引。所以我的问题是，我应该如何在 photo 属性旁边添加类似以下信息的内容：index: 2 或 index: 6 等。所以我想 return 像这样：

Array [
      Object {
        "index": 2,
        "albumId": "someId1",
        "creationTime": "sometime",
        "duration": 0,
        "filename": "name1.jpg",
        "id": "someId1",
        "uri": "someIUri1",
      },
      Object {
        "index": 6
        "albumId": "someId2",
        "creationTime": "sometime",
        "duration": 0,
        "filename": "name2.jpg",
        "id": "id2",
        "uri": "uri2",
      },
      Object {
        "index": 10
        "albumId": "someId3",
        "creationTime": "sometime",
        "filename": "filename3.jpg",
        "uri": "uri3",
      },
     ]

Answer 1

只需添加索引：

const selectedPhotos = selectedArray.map((i) => {
  let photo = photos[i];
  photo.index = i;
  return photo;
});

Answer 2

你可以这样做

const selectedPhotos = selectedArray.map((i) => {
 let curItem={...photos[i]};
 curItem.index=i;
  return curItem;
});

Answer 3

您可以创建一个新对象并在其中解构您想要的对象，然后添加索引。这样你就可以在一行中完成并且很容易阅读。

const selectedPhotos = selectedArray.map(i => ({ ...photos[i], index: i }));

更安全的版本 optional chaning:

const selectedPhotos = selectedArray.map(i => ({ ...photos?.[i], index: i }));

如何使用 map 函数，以便将索引作为属性添加到新构造的对象中？

How do I use map function, so I can add the index as a property to the newly constructed object?

javascript

reactjs

react-native

如何使用 map 函数，以便将索引作为 属性 添加到新构造的对象中？

How do I use map function, so I can add the index as a property to the newly constructed object?

javascript

reactjs

react-native

如何使用 map 函数，以便将索引作为属性添加到新构造的对象中？