Question

假设我有一个JSON对象数组，如下所示：

[{  "id": 1,
    "name": "Leanne Graham",
    "username": "Bret",
    "email": "Sincere@april.biz",
    "address": {
    "suite": "Apt. 556",
      "city": "Gwenborough",
      "zipcode": "92998-3874",
      "geo": {
        "lat": "-37.3159",
        "lng": "81.1496"
      }
    },
    "company": {
      "name": "Romaguera-Crona",
      "catchPhrase": "Multi-layered client-server neural-net",
      "bs": "harness real-time e-markets"
    },
    "hobbies":['cricket', 'football']},{
    "id": 2,
    "name": "Graham",
    "username": "David",
    "email": "Sincere@april.biz",
    "address": {
      "street": "Kulas Light",
      "suite": "Apt. 556",
      "city": "San Jose",
      "zipcode": "92998-3874",
      "geo": {
        "lat": "39.3159",
        "lng": "121.1496"
      }
    },
    "phone": ["1-770-736-8031 x56442", "4087917884", "4089088939"],
    "website": "hildegard.org",
    "dept":[{"name":"divya", "address":"abc"},{"name":"divya1", "address":"abc1"}],
    "hobbies":['baseball']}]

现在我想根据特定键获取数据，键也可以是嵌套键。让我们举一个例子，我只想获得这些密钥的数据：'name'，'username'，'city'，'lat'，'lng'。所以输出结果如下：

[{
   name:'Leanne Graham', 
   username:'Bret', 
   address.city:'Gwenborough', 
   address.geo.lat:"-37.3159",
   address.geo.lng: "81.1496"
 },
 {
   name:'Graham', 
   username:'David', 
   address.city:'San Jose', 
   address.geo.lat:"39.3159",
   address.geo.lng: "121.1496
}]

任何人都可以告诉我如何在NodeJS上执行此操作吗？

Answer 1

如果您愿意安装依赖项，则可以查找lodash.get;

npm i --save lodash.get

这将允许您：

const _get = require('lodash.get');

_get(obj, 'address.city'); // "San Jose"

使用此实用程序，您可以更轻松地查询对象的特定键/值，并根据您的要求组合自定义对象。

否则，您可以创建自己的安全访问器功能：

function getKey(key, obj) {
  return key.split('.').reduce(function(a,b){
    return a && a[b];
  }, obj);
}

getKey('address.city'', obj); // "San Jose"

Answer 2

执行复杂数据查询的最简单方法是依赖数据存储引擎，该引擎支持足够丰富的查询语言以满足您的需求。 Mongo，Couchbase和Elasticsearch是内置全功能查询语言的存储引擎示例。

另一种方法是使用像Lodash或Ramda这样的函数库来构建数据提取管道。

使用Lodash从您提供的数据示例中提取：

const _ = require('lodash')

// paths to extract from matching records

const field_paths = [
  'name', 
  'username', 
  'address.city', 
  'address.geo.lat', 
  'address.geo.lng']

// extract value at field_paths and add to result

const extract_fields = (rec) => {
  let res = {}
  field_paths.forEach((path) => {
    res[path] = _.get(rec, path)
  })
  return res
}

// query for all records where 
// name is like "*Graham*" irrespective of letter case.
// 
// and extract required fields from matching records

const results = _(data)
  .filter((rec) => _.get(rec, 'name').match(/\bgraham\b/i))
  .map(extract_fields)
  .value()

console.log(results)

将打印：

[ { name: 'Leanne Graham',
    username: 'Bret',
    'address.city': 'Gwenborough',
    'address.geo.lat': '-37.3159',
    'address.geo.lng': '81.1496' },
  { name: 'Graham',
    username: 'David',
    'address.city': 'San Jose',
    'address.geo.lat': '39.3159',
    'address.geo.lng': '121.1496' } ]

仅在Nodejs中查询特定键的嵌套JSON数组

2 个答案: