比较 NodeJs 和 Express 中的两个 JSON答案

【问题标题】：Comparing two JSONs in NodeJs & Express比较 NodeJs 和 Express 中的两个 JSON
【发布时间】：2020-01-17 21:17:02
【问题描述】：

我正在尝试比较 NodeJs 中的两个 JSONs 文件。如果有与地点 ID 匹配的评论，我需要将评论数据推送到地点 JSON 中。如果没有匹配的评论，它会推送一个空数组。

代码如下：

//放置 JSON

[{
        "id": 1,
        "title": "Hotel in Sidney",
        "maxNumberOfGuests": 5,
        "description": "Quiet place by the water.",
        "createdAt": "2019/12/7 14:34",
        "price": 120
    },
    {
        "id": 2,
        "title": "Cabin in Italy",
        "maxNumberOfGuests": 2,
        "description": "Romantic lake cabin for two.",
        "createdAt": "2019/4/7 10:00",
        "price": 250
    }
]

//审查 JSON

[{
        "id": 1,
        "numberOfStars": 3,
        "content": "Comfy place",
        "placeId": 1,
        "createdAt": 12345
    },
    {
        "id": 2,
        "numberOfStars": 4,
        "content": "Awesome lake view.",
        "placeId": "",
        "createdAt": 23456
    }
]

这是想要的结果：

[{
        "id": 1,
        "title": "Hotel in Sidney",
        "maxNumberOfGuests": 5,
        "description": "Quiet place by the water.",
        "createdAt": "2019/12/7 14:34",
        "reviews": [{
            "id": 1,
            "numberOfStars": 3,
            "content": "Comfy place",
            "placeId": 1,
            "createdAt": 12345
        }],
        "price": 120
    },
    {
        "id": 2,
        "title": "Cabin in Italy",
        "maxNumberOfGuests": 2,
        "description": "Romantic lake cabin for two.",
        "createdAt": "2019/4/7 10:00",
        "reviews": [],
        "price": 250
    }
]

这是我能走多远：

places.forEach(p => {
  const { id } = p;
  console.log(id);
  return id;
});

reviews.forEach(r => {
  const { id, numberOfStars, content, placeId, createdAt } = r;
  // console.log(id, numberOfStars, content, placeId, createdAt);
  console.log(r);
  return r;
});

//node express routes to places where will display the desired result. 

router.get('/places', function(req, res) {
  res.json(places);
});

我无法让它工作，需要一些帮助。

提前致谢。

【问题讨论】：

标签： javascript node.js json express

【解决方案1】：

试试这个

let places =[{
        "id": 1,
        "title": "Hotel in Sidney",
        "maxNumberOfGuests": 5,
        "description": "Quiet place by the water.",
        "createdAt": "2019/12/7 14:34",
        "price": 120
    },
    {
        "id": 2,
        "title": "Cabin in Italy",
        "maxNumberOfGuests": 2,
        "description": "Romantic lake cabin for two.",
        "createdAt": "2019/4/7 10:00",
        "price": 250
    }
];

let reviews =[{
        "id": 1,
        "numberOfStars": 3,
        "content": "Comfy place",
        "placeId": 1,
        "createdAt": 12345
    },
    {
        "id": 2,
        "numberOfStars": 4,
        "content": "Awesome lake view.",
        "placeId": "",
        "createdAt": 23456
    }
];
places.forEach(function(place) {
  place.reviews = reviews.filter(review => review.placeId ===place.id);
});


console.log(places);

【讨论】：

【解决方案2】：

我首先将reviews 数组缩减为一个以placeId 为键的对象。

const reviews = [{
    "id": 1,
    "numberOfStars": 3,
    "content": "Comfy place",
    "placeId": 1,
    "createdAt": 12345
  },
  {
    "id": 2,
    "numberOfStars": 4,
    "content": "Awesome lake view.",
    "placeId": "",
    "createdAt": 23456
  }
];

const reviewsHashmap = reviews.reduce((acc, review) => {
  if (!review.placeId) return acc;
  acc[review.placeId] = acc[review.placeId] || [];
  acc[review.placeId].push(review);
  return acc;
}, {})

这使得添加评论属性时性能更高，因为现在您不需要为每个地方一次又一次地过滤评论数组。

const places = [
  {
    "id": 1,
    "title": "Hotel in Sidney",
    "maxNumberOfGuests": 5,
    "description": "Quiet place by the water.",
    "createdAt": "2019/12/7 14:34",
    "price": 120
  },
  {
    "id": 2,
    "title": "Cabin in Italy",
    "maxNumberOfGuests": 2,
    "description": "Romantic lake cabin for two.",
    "createdAt": "2019/4/7 10:00",
    "price": 250
  }
];

const placesWithReviews = places.map(place => ({
  ...place,
  reviews: reviewsHashmap[place.id] || []
}))

现在您应该拥有原始的 places 数组，但每个位置都有一个额外的 reviews 属性。

【讨论】：