如何检查动态数组是否为空？

时间：2017-12-14 01:22:18

标签： javascript

您能否请看下面的代码片段，让我知道如何检查Mapped对象是否为空？ 基本上我需要做的是检查data中是否有任何保险丝阵列？如果不？然后再做一些事情

 if(e.attributes.display=='Fuses') {
   if((e.attributes.display == 'Fuses').length == 0){
      console.log("No Data For Fuses");
   }else{
      fuses.push([e.geometry.x,e.geometry.y]);
      }
}


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=[];
fuses=[];

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=='Fuses') {
   if((e.attributes.display == 'Fuses').length == 0){
      console.log("No Data For Fuses");
   }else{
      fuses.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, fuses);

2 个答案:

答案 0 :(得分：1)

下面的函数将使用reduce建立一个数组对象（一个用于保险丝，一个用于服务点，一个用于变换器），并按原样推入线圈。完成后，您可以轻松检查保险丝阵列.length === 0，如果是，请执行您需要的操作

function process() {
    data.forEach((el) => {
        let arrays = el.features.reduce(function(result, feature) {
            if (feature.attributes && feature.attributes.display) {
                // Get the display name to use as the key for our object
                let key = feature.attributes.display.replace(" ", "") 
                // Push the coords into the array
                result[key].push([feature.geometry.x, feature.geometry.y]);
            }
            return result;
        }, {
            // Provide a default object with empty arrays
            Transformer: [],
            Fuses: [],
            ServicePoint: []
        });

        console.log(arrays);

        if (arrays.Fuses.length === 0) {
            // Do what you need to here.
            console.log("No fuses");
        }
    });
}

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
                }
            }
        ]
    }
];


process();

答案 1 :(得分：1)

如果需要检查每个数据元素的保险丝，可按以下步骤进行操作

data.forEach(function(el) {
  var hasFuses = el.features.some((e) => e.attributes.display === 'Fuses');
  console.log('has: ' + hasFuses);

  el.features.forEach(function(e) {
    if (!hasFuses) {
      console.log("No Data For Fuses");
    }
    switch (e.attributes.display) {
      case 'Transformer':
        transformers.push([e.geometry.x, e.geometry.y]);
        break;
      case 'Fuses':
        fuses.push([e.geometry.x, e.geometry.y]);
        break;
      case 'Service Point':
        service_points.push([e.geometry.x, e.geometry.y]);
        break;
    }
  });
});

console.log(transformers, service_points, fuses);
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