如何从javascript中的嵌套对象数组中获取对象答案

【问题标题】：How to get object from nested object array in javascript如何从javascript中的嵌套对象数组中获取对象
【发布时间】：2019-04-15 04:04:14
【问题描述】：

我想知道如何使用javascript在输入对象中返回基于country_name的对象。输入对象为sampleobj 和变量source，作为参数传递给函数，该函数又应使用javascript 返回基于source 的输出obj，

我在下面试过这个

var source="TH";
var result = filterData(sampleobj, source);
function filterData(inputobj, src){
var filterByCountry = inputobj.filter((e)=>e.country_from.country.includes(src));
return filterByCountry;
}

var sampleobj = [
   {
     id: "trans",
     country_from: [
       {
         country: "SG"
         currency: ["SGD", "USD"]
       },
       {
         country: "TH"
         currency: ["THB", "USD"]
       }

     ]
   },
    {
     id: "fund",
     country_from: [
       {
         country: "TH"
         currency: ["THB", "USD"]
       },
       {
         country: "UK"
         currency: ["GBP", "USD"]
       }
     ]
   }
]

预期输出：

result =[{
     id: "trans",
     country_from: [
       {
         country: "TH"
         currency: ["THB", "USD"]
       }
     ]
},
{
     id: "fund",
     country_from: [
       {
         country: "TH"
         currency: ["THB", "USD"]
       }
     ]
}]

【问题讨论】：

标签： javascript jquery arrays object

【解决方案1】：

您可以使用map 和filter

使用过滤器，我们只取出匹配的country 并将其作为country_from's 值放回

let sampleobj = [{id: "trans",country_from: [{country: "SG",currency: ["SGD", "USD"]},{country: "TH",currency: ["THB", "USD"]}]},
{id: "fund",country_from: [{country: "TH",currency: ["THB", "USD"]},{country: "UK",currency: ["GBP", "USD"]}]}]

const source = 'TH'

const op = sampleobj.map(inp=>{
  const country_from = inp.country_from.filter(({country})=> country === source)
  return {
    ...inp,
    country_from
  }  
})

console.log(op)

【讨论】：

【解决方案2】：

您可以使用map 和filter 的组合。 map 将返回一个新数组，并在 map 回调函数中创建并返回一个带有键 id 和 country_from 的对象。在填充country_from 的值时，使用filter 仅提取国家为“TH”的对象

var sampleobj = [{
    id: "trans",
    country_from: [{
        country: "SG",
        currency: ["SGD", "USD"]
      },
      {
        country: "TH",
        currency: ["THB", "USD"]
      }

    ]
  },
  {
    id: "fund",
    country_from: [{
        country: "TH",
        currency: ["THB", "USD"]
      },
      {
        country: "UK",
        currency: ["GBP", "USD"]
      }
    ]
  }
]

let result = sampleobj.map(function(item) {

  return {
    id: item.id,
    country_from: item.country_from.filter(function(elem) {
      return elem.country === 'TH'
    })
  }
})
console.log(result)

【讨论】：

【解决方案3】：

您可以使用map 循环遍历数组并使用filter 过滤country_from

var sampleobj = [{"id":"trans","country_from":[{"country":"SG","currency":["SGD","USD"]},{"country":"TH","currency":["THB","USD"]}]},{"id":"fund","country_from":[{"country":"TH","currency":["THB","USD"]},{"country":"UK","currency":["GBP","USD"]}]}];

var source = "TH";
let result = sampleobj.map(({id,country_from}) =>  ({id,country_from: country_from.filter(o => o.country === source)}));

console.log(result);

您可以添加另一个filter() 以仅返回带有country_from 的对象

var sampleobj = [{
    "id": "trans",
    "country_from": [{
      "country": "SG",
      "currency": ["SGD", "USD"]
    }, {
      "country": "TH",
      "currency": ["THB", "USD"]
    }]
  },
  {
    "id": "fund",           //Will not be returned since no TH on country_from
    "country_from": [{
      "country": "ID",
      "currency": ["THB", "USD"]
    }, {
      "country": "UK",
      "currency": ["GBP", "USD"]
    }]
  } 
]

var source = "TH";
let result = sampleobj.map(({id,country_from}) => ({id,country_from: country_from.filter(o => o.country === source)}))
  .filter(o => o.country_from.length);

console.log(result);

【讨论】：

【解决方案4】：

使用 Map & Filter 并更改功能如下：

function filterData(inputobj, src) {
        var filterByCountry = inputobj.map(({
            id, country_from
        }) => ({
            id, country_from: country_from.filter(obj => obj.country.includes(src))
        }));
        return filterByCountry;
    }
     var sampleobj = [
            {
                id: "trans"
                , country_from: [
                    {
                        country: "SG"
                        , currency: ["SGD", "USD"]
       }
                    , {
                        country: "TH"
                        , currency: ["THB", "USD"]
       }

     ]
   }
            , {
                id: "fund"
                , country_from: [
                    {
                        country: "TH"
                        , currency: ["THB", "USD"]
       }
                    , {
                        country: "UK"
                        , currency: ["GBP", "USD"]
       }
     ]
   }
]
        var source = "TH";
        var result = filterData(sampleobj, source);
        console.log(result)

【讨论】：