lodash 从数组中选取对象字段

Question

我有对象数组：

var results= [
    {         
      "_type": "MyType",
      "_id": "57623535a44b8f1417740a13",         
      "_source": {
        "info": {
          "year": 2010,
          "number": "string",             
        },
        "type": "stolen",           
        "date": "2016-06-16T00:00:00",
        "createdBy": "57469f3c71c8bf2479d225a6"            
      }
    }
  ];

我需要 select 数组中的特定字段。结果，我想得到以下内容：

[
    {
        "_id": "57623535a44b8f1417740a13",
        "info": {
            "year": 2010,
            "number": "string"
        },
        "type": "stolen",            
        "date": "2016-06-16T00:00:00",
        "createdBy": "57469f3c71c8bf2479d225a6"
    }
]

如您所见，我想要 select _id 字段和 _source 对象的内容。我如何使用 lodash 做到这一点？

我找到了 .map 函数，但它不接受键数组： var res = _.map(results, "_source");

Answer 1

在简单的 Javascript 中，您可以使用 Array#map 和 assemble 为每个对象迭代一个新对象，而不会破坏原始对象。

var results = [{ "_type": "MyType", "_id": "57623535a44b8f1417740a13", "_source": { "info": { "year": 2010, "number": "string", }, "type": "stolen", "date": "2016-06-16T00:00:00", "createdBy": "57469f3c71c8bf2479d225a6" } }],
    res = results.map(function (a) {
        var o = { _id: a._id };
        ["info", "type", "date", "createdBy"].forEach(function (k) {
            o[k] = a._source[k];
        });
        return o;
    });

console.log(res);

Answer 2

var results = [{
  _type: "MyType",
  _id: "57623535a44b8f1417740a13",
  _source: {
    info: {
      year: 2010,
      number: "string",
    },
    type: "stolen",
    date: "2016-06-16T00:00:00",
    createdBy: "57469f3c71c8bf2479d225a6"
  }
}];

var rootProperty = ['_id']
var innerProperty = '_source'

var myArray = _.map(results, result => _(result)
  .pick(rootProperty)
  .assign(_.result(result, innerProperty))
  .value()
)

console.log(myArray)

.as-console-wrapper { max-height: 100% !important; top: 0; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Answer 3

您可以 map() the result and have each item assign() 对象中的 _id 键值与 _source 对象一起使用。

results = _.map(results, item => _.assign(
  { _id: item._id }, 
  item._source
));

var results = [{
  "_type": "MyType",
  "_id": "57623535a44b8f1417740a13",
  "_source": {
    "info": {
      "year": 2010,
      "number": "string",
    },
    "type": "stolen",
    "date": "2016-06-16T00:00:00",
    "createdBy": "57469f3c71c8bf2479d225a6"
  }
}];

results = _.map(results, item => _.assign(
  { _id: item._id }, 
  item._source
));

document.write('<pre>' + JSON.stringify(results, 0, 4) + '</pre>');

<script src="https://cdn.jsdelivr.net/lodash/4.13.1/lodash.min.js"></script>

您也可以选择用纯 JS 编写：

result = results.map(item => Object.assign(
  { _id: item._id }, item._source
));

var results = [{
  "_type": "MyType",
  "_id": "57623535a44b8f1417740a13",
  "_source": {
    "info": {
      "year": 2010,
      "number": "string",
    },
    "type": "stolen",
    "date": "2016-06-16T00:00:00",
    "createdBy": "57469f3c71c8bf2479d225a6"
  }
}];

result = results.map(item => Object.assign(
  { _id: item._id }, item._source
));

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 4

你可以这样做：

var mapped = _.map(results, _.partialRight(_.pick, ['_id', 'info', 'type', 'date', 'createdBy']));

一点解释：

_.map()：需要一个函数，该函数从集合中获取每个项目，以便您可以将其映射到其他对象。
_.partialRight()：接受一个函数，稍后将调用它的参数附加到末尾
_.pick(): 从对象中获取指定的路径。

Answer 5

我有同样的要求，下面的解决方案最适合我。

let users = [
{
  "_id": "5ead7783ed74d152f86de7b0",
  "first_name": "User First name 1",
  "last_name": "User Last name 1",
  "email": "user1@example.com",
  "phone": 9587788888
},
{
  "_id": "5ead7b780d4bc43fd0ef92e7",
  "first_name": "User FIRST name 1",
  "last_name": "User LAST name 1",
  "email": "user2@example.com",
  "phone": 9587788888
}
 ];

users = users.map(user => _.pick(user,['_id','first_name']))

console.log(users)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

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