如何通过选择对象中的特定属性来使用Map功能

Question

拥有像data这样的动态对象，请您告诉我有没有办法可以像这样映射数据：

我需要的是使用特定值geometry和Transformer对所有属性进行Service Point，并将它们加载到数组中。

var transformers = [
                    [-88.17602806699995, 41.78431233100008],
                    [-88.17546081099994, 41.783341919000065]
                   ]

或

var servicePoints = [
                    [-88.17599727899994, 41.78465526100007],
                    [-88.17595382899998, 41.78455803400004],
                    [-88.17582231499995, 41.78435312600004],
                    [-88.17561004899994, 41.78400533500074],
                    [-88.17557576699994, 41.78393182000008],
                    [-88.17535967199996, 41.78352876900004]
                   ]

这是数据集

var data = [{
    "displayFieldName": "",
    "fieldAliases": {
      "OBJECTID": "OBJECTID"
    },
    "fields": [{
      "name": "OBJECTID",
      "type": "esriFieldTypeOID",
      "alias": "OBJECTID"
    }],
    "features": [{
        "attributes": {
          "OBJECTID": 649
        }
      },
      {
        "attributes": {
          "OBJECTID": 665
        }
      },
      {
        "attributes": {
          "OBJECTID": 762
        }
      }
    ]
  },
  {
    "displayFieldName": "",
    "fieldAliases": {
      "display": "display",
      "OBJECTID": "OBJECTID"
    },
    "geometryType": "esriGeometryPoint",
    "spatialReference": {
      "wkid": 4326,
      "latestWkid": 4326
    },
    "fields": [{
        "name": "display",
        "type": "esriFieldTypeString",
        "alias": "display",
        "length": 50
      },
      {
        "name": "OBJECTID",
        "type": "esriFieldTypeOID",
        "alias": "OBJECTID"
      }
    ],
    "features": [{
        "attributes": {
          "display": "Transformer",
          "OBJECTID": 1537
        },
        "geometry": {
          "x": -88.17602806699995,
          "y": 41.78431233100008
        }
      },
      {
        "attributes": {
          "display": "Transformer",
          "OBJECTID": 1591
        },
        "geometry": {
          "x": -88.17546081099994,
          "y": 41.783341919000065
        }
      }
    ]
  },
  {
    "displayFieldName": "",
    "fieldAliases": {
      "display": "display",
      "OBJECTID": "OBJECTID"
    },
    "geometryType": "esriGeometryPoint",
    "spatialReference": {
      "wkid": 4326,
      "latestWkid": 4326
    },
    "fields": [{
        "name": "display",
        "type": "esriFieldTypeString",
        "alias": "display",
        "length": 50
      },
      {
        "name": "OBJECTID",
        "type": "esriFieldTypeOID",
        "alias": "OBJECTID"
      }
    ],
    "features": [{
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13597
        },
        "geometry": {
          "x": -88.17599727899994,
          "y": 41.78465526100007
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13598
        },
        "geometry": {
          "x": -88.17595382899998,
          "y": 41.78455803400004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13599
        },
        "geometry": {
          "x": -88.17582231499995,
          "y": 41.78435312600004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13600
        },
        "geometry": {
          "x": -88.17561004899994,
          "y": 41.784005335000074
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13601
        },
        "geometry": {
          "x": -88.17557576699994,
          "y": 41.78393182000008
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13602
        },
        "geometry": {
          "x": -88.17535967199996,
          "y": 41.78352876900004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13603
        },
        "geometry": {
          "x": -88.17534426199995,
          "y": 41.78340020400003
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13649
        },
        "geometry": {
          "x": -88.17450698899995,
          "y": 41.78350136200004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13650
        },
        "geometry": {
          "x": -88.17435162999999,
          "y": 41.783597986000075
        }
      }
    ]
  }
];

我已经尝试过了：

var transformers = data.map((obj) => obj.features.map(({attributes})=>attributes.display || "NONE"));

但这只会在没有几何体的不同数组中返回它们！

Answer 1

您可以循环遍历data中所有对象的所有功能，并随时累积结果：

function get(data, attributeType) {
    return data.reduce(function(acc, obj) {                               // for each object obj in the array data
        obj.features.forEach(function(feature) {                          // for each feature feature in the array features of obj
            if(feature.attributes                                         // if this feature has an attributes property
               && typeof feature.attributes === "object"                  // and that attributes property is an object
               && feature.attributes.display === attributeType) {         // and the display property of this feature's attributes is the same as attributeType
                acc.push([feature.geometry.x, feature.geometry.y]);       // then push the coordinates of its geometry coordinates to acc
            }
        });
        return acc;
    }, []);
}

然后为了得到变形，你打电话就是这样：

var transformers = get(data, "Transformer");

并获得服务指针，你可以这样称呼它：

var servicePoints = get(data, "Service Point");

示例：

function get(data, attributeType) {
    return data.reduce(function(acc, obj) {                               // for each object obj in the array data
        obj.features.forEach(function(feature) {                          // for each feature feature in the array features of obj
            if(feature.attributes                                         // if this feature has an attributes property
               && typeof feature.attributes === "object"                  // and that attributes property is an object
               && feature.attributes.display === attributeType) {         // and the display property of this feature's attributes is the same as attributeType
                acc.push([feature.geometry.x, feature.geometry.y]);       // then push the coordinates of its geometry coordinates to acc
            }
        });
        return acc;
    }, []);
}

var data = [{"displayFieldName":"","fieldAliases":{"OBJECTID":"OBJECTID"},"fields":[{"name":"OBJECTID","type":"esriFieldTypeOID","alias":"OBJECTID"}],"features":[{"attributes":{"OBJECTID":649}},{"attributes":{"OBJECTID":665}},{"attributes":{"OBJECTID":762}}]},{"displayFieldName":"","fieldAliases":{"display":"display","OBJECTID":"OBJECTID"},"geometryType":"esriGeometryPoint","spatialReference":{"wkid":4326,"latestWkid":4326},"fields":[{"name":"display","type":"esriFieldTypeString","alias":"display","length":50},{"name":"OBJECTID","type":"esriFieldTypeOID","alias":"OBJECTID"}],"features":[{"attributes":{"display":"Transformer","OBJECTID":1537},"geometry":{"x":-88.17602806699995,"y":41.78431233100008}},{"attributes":{"display":"Transformer","OBJECTID":1591},"geometry":{"x":-88.17546081099994,"y":41.783341919000065}}]},{"displayFieldName":"","fieldAliases":{"display":"display","OBJECTID":"OBJECTID"},"geometryType":"esriGeometryPoint","spatialReference":{"wkid":4326,"latestWkid":4326},"fields":[{"name":"display","type":"esriFieldTypeString","alias":"display","length":50},{"name":"OBJECTID","type":"esriFieldTypeOID","alias":"OBJECTID"}],"features":[{"attributes":{"display":"Service Point","OBJECTID":13597},"geometry":{"x":-88.17599727899994,"y":41.78465526100007}},{"attributes":{"display":"Service Point","OBJECTID":13598},"geometry":{"x":-88.17595382899998,"y":41.78455803400004}},{"attributes":{"display":"Service Point","OBJECTID":13599},"geometry":{"x":-88.17582231499995,"y":41.78435312600004}},{"attributes":{"display":"Service Point","OBJECTID":13600},"geometry":{"x":-88.17561004899994,"y":41.784005335000074}},{"attributes":{"display":"Service Point","OBJECTID":13601},"geometry":{"x":-88.17557576699994,"y":41.78393182000008}},{"attributes":{"display":"Service Point","OBJECTID":13602},"geometry":{"x":-88.17535967199996,"y":41.78352876900004}},{"attributes":{"display":"Service Point","OBJECTID":13603},"geometry":{"x":-88.17534426199995,"y":41.78340020400003}},{"attributes":{"display":"Service Point","OBJECTID":13649},"geometry":{"x":-88.17450698899995,"y":41.78350136200004}},{"attributes":{"display":"Service Point","OBJECTID":13650},"geometry":{"x":-88.17435162999999,"y":41.783597986000075}}]}];


var transformers = get(data, "Transformer");
var servicePoints = get(data, "Service Point");

console.log("Transformers:", transformers);
console.log("servicePoints:", servicePoints);

Answer 2

可能这可以用更好的方式完成（map，filter，reduce ...？），但是两个forEach（）循环也可以完成这项任务：

transformers=[];
service_points=[];

data.forEach(function(el) {
 el.features.forEach(function(e) {
  if(e.attributes.display) {
   if(e.attributes.display=='Transformer') {
      transformers.push([e.geometry.x,e.geometry.y]);
}
  if(e.attributes.display=='Service Point') {
      service_points.push([e.geometry.x,e.geometry.y]);
}
}
});
});

console.log(transformers,service_points);

演示：

var data = [{
    "displayFieldName": "",
    "fieldAliases": {
      "OBJECTID": "OBJECTID"
    },
    "fields": [{
      "name": "OBJECTID",
      "type": "esriFieldTypeOID",
      "alias": "OBJECTID"
    }],
    "features": [{
        "attributes": {
          "OBJECTID": 649
        }
      },
      {
        "attributes": {
          "OBJECTID": 665
        }
      },
      {
        "attributes": {
          "OBJECTID": 762
        }
      }
    ]
  },
  {
    "displayFieldName": "",
    "fieldAliases": {
      "display": "display",
      "OBJECTID": "OBJECTID"
    },
    "geometryType": "esriGeometryPoint",
    "spatialReference": {
      "wkid": 4326,
      "latestWkid": 4326
    },
    "fields": [{
        "name": "display",
        "type": "esriFieldTypeString",
        "alias": "display",
        "length": 50
      },
      {
        "name": "OBJECTID",
        "type": "esriFieldTypeOID",
        "alias": "OBJECTID"
      }
    ],
    "features": [{
        "attributes": {
          "display": "Transformer",
          "OBJECTID": 1537
        },
        "geometry": {
          "x": -88.17602806699995,
          "y": 41.78431233100008
        }
      },
      {
        "attributes": {
          "display": "Transformer",
          "OBJECTID": 1591
        },
        "geometry": {
          "x": -88.17546081099994,
          "y": 41.783341919000065
        }
      }
    ]
  },
  {
    "displayFieldName": "",
    "fieldAliases": {
      "display": "display",
      "OBJECTID": "OBJECTID"
    },
    "geometryType": "esriGeometryPoint",
    "spatialReference": {
      "wkid": 4326,
      "latestWkid": 4326
    },
    "fields": [{
        "name": "display",
        "type": "esriFieldTypeString",
        "alias": "display",
        "length": 50
      },
      {
        "name": "OBJECTID",
        "type": "esriFieldTypeOID",
        "alias": "OBJECTID"
      }
    ],
    "features": [{
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13597
        },
        "geometry": {
          "x": -88.17599727899994,
          "y": 41.78465526100007
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13598
        },
        "geometry": {
          "x": -88.17595382899998,
          "y": 41.78455803400004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13599
        },
        "geometry": {
          "x": -88.17582231499995,
          "y": 41.78435312600004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13600
        },
        "geometry": {
          "x": -88.17561004899994,
          "y": 41.784005335000074
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13601
        },
        "geometry": {
          "x": -88.17557576699994,
          "y": 41.78393182000008
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13602
        },
        "geometry": {
          "x": -88.17535967199996,
          "y": 41.78352876900004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13603
        },
        "geometry": {
          "x": -88.17534426199995,
          "y": 41.78340020400003
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13649
        },
        "geometry": {
          "x": -88.17450698899995,
          "y": 41.78350136200004
        }
      },
      {
        "attributes": {
          "display": "Service Point",
          "OBJECTID": 13650
        },
        "geometry": {
          "x": -88.17435162999999,
          "y": 41.783597986000075
        }
      }
    ]
  }
];

transformers=[];
service_points=[];

data.forEach(function(el) {
 el.features.forEach(function(e) {
  if(e.attributes.display) {
   if(e.attributes.display=='Transformer') {
      transformers.push([e.geometry.x,e.geometry.y]);
}
  if(e.attributes.display=='Service Point') {
      service_points.push([e.geometry.x,e.geometry.y]);
}
}
});
});

console.log(transformers,service_points);