計算特定的對象屬性值（如果它們匹配）

Question

我想計算匹配對象屬性值的數量。 更具體地講，如果我的結果object.place_name相同，則將下一項繼續計算，將其全部累加，然后使用res.render將此結果傳遞到前端

當前對象

     results = [ { id: 'country.8605848117814600',
    type: 'Feature',
    place_type: [ 'country'
    ],
    relevance: 1,
    properties: { short_code: 'gb', wikidata: 'Q145'
    },
    text: 'United Kingdom',
    place_name: 'United Kingdom',
    bbox: [
        -8.718659,
        49.802665,
        1.867399,
        60.945453
    ],
    center: [
        -2,
        54
    ],
    geometry: { type: 'Point', coordinates: [Array
        ]
    }
},
{ id: 'country.12399313490269000',
    type: 'Feature',
    place_type: [ 'country'
    ],
    relevance: 1,
    properties: { short_code: 'dk', wikidata: 'Q35'
    },
    text: 'Denmark',
    place_name: 'Denmark',
    bbox: [
        7.970276,
        54.3991486,
        15.253716,
        57.9322004
    ],
    center: [
        10,
        56
    ],
    geometry: { type: 'Point', coordinates: [Array
        ]
    }
},
{ id: 'country.12399313490269000',
    type: 'Feature',
    place_type: [ 'country'
    ],
    relevance: 1,
    properties: { short_code: 'dk', wikidata: 'Q35'
    },
    text: 'Denmark',
    place_name: 'Denmark',
    bbox: [
        7.970276,
        54.3991486,
        15.253716,
        57.9322004
    ],
    center: [
        10,
        56
    ],
    geometry: { type: 'Point', coordinates: [Array
        ]
    }
},
{ id: 'country.8605848117814600',
    type: 'Feature',
    place_type: [ 'country'
    ],
    relevance: 1,
    properties: { short_code: 'gb', wikidata: 'Q145'
    },
    text: 'United Kingdom',
    place_name: 'United Kingdom',
    bbox: [
        -8.718659,
        49.802665,
        1.867399,
        60.945453
    ],
    center: [
        -2,
        54
    ],
    geometry: { type: 'Point', coordinates: [Array
        ]
    }
}
]

我正在嘗試運行的代碼

    const promises = results.map(result =>

      Promise.all([
        geoPromise(result.Country_Name),
        geoPromise(result.Organisation_Name),
        result.Output_Title_Name
      ])

    );



    Promise.all(promises)
      .then((values) => {
        let results = values.map(elmt => elmt[0]);
        console.log(results)
        let businesses = values.map(elmt => elmt[1]);


        let names = values.map(elmt => elmt[2]);

         place_name = ['Denmark', 'United Kingdom']
  count = results.reduce((s, o) => s + (o.place_name === place_name[0]), 0);

  countObject = {place_name:'',
                 count:''}

                 countObject.place_name = place_name[0]
                 countObject.count = count
  console.log(countObject)

        res.render('layouts/layout', {
          results: JSON.stringify(results),
          businesses: JSON.stringify(businesses),
          names: JSON.stringify(names),
          resultCount: resultCount
        });
      })

但是，我的resultCount僅返回一個空數組。 有人可以描述我想要做的更好的方法嗎？

Answer 1

您可以使用Array#reduce並計算條件是否使用來自對象的值和給定值得出的true值。

 var results = [{ id: 'country.8605848117814600', type: 'Feature', place_type: ['country'], relevance: 1, properties: { short_code: 'gb', wikidata: 'Q145' }, text: 'United Kingdom', place_name: 'United Kingdom', bbox: [-8.718659, 49.802665, 1.867399, 60.945453], center: [-2, 54], geometry: { type: 'Point', coordinates: [Array] } }, { id: 'country.12399313490269000', type: 'Feature', place_type: ['country'], relevance: 1, properties: { short_code: 'dk', wikidata: 'Q35' }, text: 'Denmark', place_name: 'Denmark', bbox: [7.970276, 54.3991486, 15.253716, 57.9322004], center: [10, 56], geometry: { type: 'Point', coordinates: [Array] } }, { id: 'country.12399313490269000', type: 'Feature', place_type: ['country'], relevance: 1, properties: { short_code: 'dk', wikidata: 'Q35' }, text: 'Denmark', place_name: 'Denmark', bbox: [7.970276, 54.3991486, 15.253716, 57.9322004], center: [10, 56], geometry: { type: 'Point', coordinates: [Array] } }, { id: 'country.8605848117814600', type: 'Feature', place_type: ['country'], relevance: 1, properties: { short_code: 'gb', wikidata: 'Q145' }, text: 'United Kingdom', place_name: 'United Kingdom', bbox: [-8.718659, 49.802665, 1.867399, 60.945453], center: [-2, 54], geometry: { type: 'Point', coordinates: [Array] } }]; place_name = 'Denmark', count = results.reduce((s, o) => s + (o.place_name === place_name), 0); console.log(count);