如何将2个JSON对象中的特定值添加到新的JSON对象中

Question

I have extracted the amount of times a country appears in an object (shown at the bottom). My problem is i need the geocode informaition to go along with they country names+amount of times the appear, so i can plot the actual result on the actual country on my map.

So from the object below, the resulting object from the mapToProp function would be

Germany:3,
United Kingdom: 1

But I need something like below. Because this is the format mapbox seemingly expects geojson objects to be.

   {
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "geometry": {
                "type": "Point",
                "coordinates": [
                    -77.034084142948,
                    38.909671288923
                ]
            },
            "properties": {
                "name":'Germany',
                "amount": 3
            }
        },
        {
            "type": "Feature",
            "geometry": {
                "type": "Point",
                "coordinates": [
                    -77.034084142948,
                    38.909671288923
                ]
            },
            "properties": {
                "name":'United Kingdom',
                "amount": 4
            }
        }
    ]
}

Getting the country names+the amount of time they appear

   function mapToProp(data, prop) {
        return data
          .reduce((res, item) => Object
            .assign(res, {
              [item[prop]]: 1 + (res[item[prop]] || 0)
            }), Object.create(null))
        ;
      }

The result returned back from the geocoder (this is what country do some specific titles appear in)

var data = [
  {
    bbox: [
      5.866003, 47.270461, 15.041428, 55.0845576
    ],
    center: [
      10, 51
    ],
    geometry: {
      coordinates:[
        10, 51
      ],
      type: "Point"
    }
  }, {
    id: "country.10743216036480410",
    place_name: "Germany",
    place_type: ["country"],
    properties: {
      short_code: "de",
      wikidata: "Q183"
    },
    relevance: 1,
    text: "Germany",
    type: "Feature"
  }, {
    bbox: [
      5.866003, 47.270461, 15.041428, 55.0845576
    ],
    center: [
      10, 51
    ],
    geometry: {
      type: "Point",
      coordinates:[
        10, 51
      ]
    },
    id: "country.10743216036480410",
    place_name: "Germany",
    place_type: ["country"],
    properties: {
      short_code: "de",
      wikidata: "Q183"
    },
    relevance: 1,
    text: "Germany",
    type: "Feature"
  }, {
    bbox: [
      5.866003, 47.270461, 15.041428, 55.0845576
    ],
    center: [
      10, 51
    ],
    geometry: {
      type: "Point",
      coordinates:[
        10, 51
      ]
    },
    id: "country.10743216036480410",
    place_name: "Germany",
    place_type: ["country"],
    properties: {
      short_code: "de",
      wikidata: "Q183"
    },
    relevance: 1,
    text: "Germany",
    type: "Feature"
  }, {
    bbox: [
      -8.718659, 49.802665, 1.867399, 60.945453
    ],
    center: [
      -2, 54
    ],
    geometry: {
      type: "Point",
      coordinates:[
        10, 51
      ],
    },
    id: "country.8605848117814600",
    place_name: "United Kingdom",
    place_type: ["country"],
    properties: {
      short_code: "gb",
      wikidata: "Q145"
    },
    relevance: 1,
    text: "United Kingdom",
    type: "Feature"
  }
]

Answer 1

EDIT:

Based on the update desired result (grouping by type then by place_name ) you could do that 2 ways...

1. Quick & dirty (more brittle)

   • since you data array only includes objects with the type === Feature , you could just add that property and return them nested in the features array...

function groupByProp(data, prop) {
    let objsByPlaceName = data.reduce((res, item) => {
            if (!item[prop]) 
                return res;
            let existing = res[item[prop]],
                amount = existing && existing.amount
                    ? existing.amount + 1
                    : 1,
                newObj = (() => {
                    if (existing && existing.geometry) 
                        return {amount, geometry: existing.geometry};
                    if (item.geometry) 
                        return {amount, geometry: item.geometry};
                    return {amount};
                })();
            return Object.assign(res, {
                [item[prop]]: newObj
            })
        }, {})

    return {
        "type": "FeatureCollection",
        "features": Object.keys(objsByPlaceName).map(key=> {
             let obj = objsByPlaceName[key];
             return {
                type: "Feature",
                geometry: obj.geometry,
                properties: {
                  name: key,
                  amount: obj.amount
                }
             }
        })
    }
}

There are more efficient way to handle this (N1 vs N^2), but that would require a lot of juggling of property names and manipulating deeply nested values. I'd recommend leaving the initial groupByProp() logic and then flattening that data into the desired structure afterwards.

2. More flexible
   • If you're expecting to group elements with different values for type then you will have to group by that property first. This actually takes quite a bit of work given the data structures so let me know if you actually want the solution before put it together.

INITAL ANSWER:

function groupByProp(data, prop) {
  return data
    .reduce((res, item) => {
      if (!item[prop]) return res;
      let existing = res[item[prop]],
          amount = existing && existing.amount ? existing.amount + 1 : 1,
          newObj = (()=> {
            if (existing && existing.geometry) return {amount, geometry: existing.geometry};
            if (item.geometry) return {amount, geometry: item.geometry};
            return {amount};
          })();
      return Object.assign(res, { [item[prop]]: newObj } )
    },{});
}

groupByProp(data, 'place_name')

This is likely close to what you're looking for except the first element in the data array you provided doesn't have a place_name property so if you wont to hanlde that differently you will have to change this line...

if (!item[prop]) return res;