有没有一种最佳方法可以根据其中一个键的值从 object 数组中返回所有值。 使用 array.reduce 或 array.forEach

Question

我正在使用县的选择来获得每个指定县的地区及其总人口。 但这并不适用于所有县，而是随机发生的。 我想从 select 选项中获取县，并返回该地区及其男性和女性的总人口。

这是代码

let selected_county = ["Lofa", "Bomi", "Bong", "River Gee", "Sinoe"];
let population =[
         { "county": "River Gee ",
            "district": "Glaro ",
            "male": 2613,
            "female": 2379
        },
        {
            "county": "River Gee ",
            "district": "Karforh ",
            "male": 3072,
            "female": 2884
        },
        {
            "county": "Lofa ",
            "district": "Nanee ",
            "male": 3421,
            "female": 2581
        },
        {
            "county": "Lofa ",
            "district": "Nyenawliken ",
            "male": 2668,
            "female": 2491
        },
        {
            "county": "Bong ",
            "district": "Nyenebo ",
            "male": 3046,
            "female": 2657
        },
        {
            "county": "Bong ",
            "district": "Potupo",
            "male": 3689,
            "female": 3648
        },
        {
            "county": "Bomi ",
            "district": "Sarbo ",
            "male": 2680,
            "female": 2640
        },
        {
            "county": "Bomi ",
            "district": "Tuobo ",
            "male": 2496,
            "female": 2372
        },
        {
            "county": "Sinoe ",
            "district": "Bodae ",
            "male": 2151,
            "female": 1388
        },
        {
            "county": "Sinoe ",
            "district": "Bokon ",
            "male": 2457,
            "female": 1916
        }]
   let district_population = { };

   population.forEach((ele)=>{
       ele.forEach((elem) => {
         if (elem.county === selected_county) { 

    //selected_county has the array of county used in the population's array

           districts_population[elem.district] = elem.male + elem.female;
   
           }
        })
    })
   console.log(districts_population);

预期 output：

"River Gee" : {{
            "district": "Karforh ",
            "male": 3072,
            "female": 2884,
             "total" : 5956
            },
            {
             "district": "Karforh ",
            "male": 3072,
            "female": 2884,
              "total": 5956
            }}
    "Lofa" :{
            {
            "district": "Nanee ",
            "male": 3421,
            "female": 2581,
             "total" : 6002
        },
        {
          "district": "Nyenawliken ",
            "male": 2668,
            "female": 2491,
            "total": 5159
        }
       }
"Bong": {{
            "district": "Nyenebo ",
            "male": 3046,
            "female": 2657,
            "total": 5159
        },
        { 
            "district": "Potupo",
            "male": 3689,
            "female": 3648,
            "total": 5159
        }
      }
"Bomi":{{
            "district": "Sarbo ",
            "male": 2680,
            "female": 2640,
            "total": 5159
        },
        {
            "district": "Tuobo ",
            "male": 2496,
            "female": 2372,
            "total": 5159
        }
      }
"Sinoe": {{ 
            "district": "Bodae ",
            "male": 2151,
            "female": 1388
            "female": 2372,
            "total": 5159
        },
        { 
            "district": "Bokon ",
            "male": 2457,
            "female": 1916
            "female": 2372,
            "total": 5159
        }
      }

//但是这个 output 只发生在少数几个县不是全部

Answer 1

看起来每个县名后面都有一个空格，这意味着它不匹配。 这是一个快速的解决方案...

 let selected_county = ["Lofa", "Bomi", "Bong", "River Gee", "Sinoe"]; let population =[ { "county": "River Gee ", "district": "Glaro ", "male": 2613, "female": 2379 }, { "county": "River Gee ", "district": "Karforh ", "male": 3072, "female": 2884 }, { "county": "Lofa ", "district": "Nanee ", "male": 3421, "female": 2581 }, { "county": "Lofa ", "district": "Nyenawliken ", "male": 2668, "female": 2491 }, { "county": "Bong ", "district": "Nyenebo ", "male": 3046, "female": 2657 }, { "county": "Bong ", "district": "Potupo", "male": 3689, "female": 3648 }, { "county": "Bomi ", "district": "Sarbo ", "male": 2680, "female": 2640 }, { "county": "Bomi ", "district": "Tuobo ", "male": 2496, "female": 2372 }, { "county": "Sinoe ", "district": "Bodae ", "male": 2151, "female": 1388 }, { "county": "Sinoe ", "district": "Bokon ", "male": 2457, "female": 1916 }] selected_county.forEach(country => { population.forEach(el => { el.county == (country + " ") && console.log(el)}) })

Answer 2

运行代码时收到错误消息，但我认为您的问题是population中的县名末尾有空格。

我不确定您是否想要 object 中的全部人口，因为您预期的 output 是不同的。 我刚刚使用了您预期的 output，但是如果您清除它，我可以将我的答案编辑为正确的 output

 let selected_county = ["Lofa", "Bomi", "Bong", "River Gee", "Sinoe"]; let population =[ { "county": "River Gee", "district": "Glaro ", "male": 2613, "female": 2379 }, { "county": "River Gee", "district": "Karforh ", "male": 3072, "female": 2884 }, { "county": "Lofa ", "district": "Nanee ", "male": 3421, "female": 2581 }, { "county": "Lofa ", "district": "Nyenawliken ", "male": 2668, "female": 2491 }, { "county": "Bong ", "district": "Nyenebo ", "male": 3046, "female": 2657 }, { "county": "Bong ", "district": "Potupo", "male": 3689, "female": 3648 }, { "county": "Bomi ", "district": "Sarbo ", "male": 2680, "female": 2640 }, { "county": "Bomi ", "district": "Tuobo ", "male": 2496, "female": 2372 }, { "county": "Sinoe ", "district": "Bodae ", "male": 2151, "female": 1388 }, { "county": "Sinoe ", "district": "Bokon ", "male": 2457, "female": 1916 }] let districts_population=population.filter(count=>selected_county.includes(count.county.trim())) console.log(districts_population);