从JSON获取信息

Question

我有一个像这样的json文件：

[
    {
        "countryName": "Austria",
        "countryID": "AT",
        "countryPopulation": 8451860,
        "regions":[
            {
                "regionName": "Burgenland (AT)",
                "regionID": "AT11",
                "regionPopulation": 286691 
            },
            {
                "regionName": "Niederösterreich",
                "regionID": "AT12",
                "regionPopulation": 1618592
            },
            {
                "regionName": "Wien",
                "regionID": "AT13",
                "regionPopulation": 1741246
            },
            {
                "regionName": "Kärnten",
                "regionID": "AT21",
                "regionPopulation": 555473 
            },
            {
                "regionName": "Steiermark",
                "regionID": "AT22",
                "regionPopulation": 1210971 
            },
            {
                "regionName": "Oberösterreich",
                "regionID": "AT31",
                "regionPopulation": 1418498 
            },
            {
                "regionName": "Salzburg",
                "regionID": "AT32",
                "regionPopulation": 531898 
            },
            {
                "regionName": "Tirol",
                "regionID": "AT33",
                "regionPopulation": 715888  
            },
            {
                "regionName": "Vorarlberg",
                "regionID": "AT34",
                "regionPopulation": 372603 
            }
        ]
    },
    {
        "countryName": "Belgium",
        "countryID": "BE",
        "countryPopulation": 11161642,
        "regions":[
            {
                "regionName": "Région de Bruxelles-Capitale",
                "regionID": "BE10",
                "regionPopulation": 1174624 
            },
            {
                "regionName": "Prov. Antwerpen",
                "regionID": "BE21",
                "regionPopulation": 1802309  
            },
            {
                "regionName": "Prov. Limburg (BE)",
                "regionID": "BE22",
                "regionPopulation": 855963 
            },
            {
                "regionName": "Prov. Oost-Vlaanderen",
                "regionID": "BE23",
                "regionPopulation": 1465150  
            },
            {
                "regionName": "Prov. Vlaams-Brabant",
                "regionID": "BE24",
                "regionPopulation": 1103737  
            },
            {
                "regionName": "Prov. West-Vlaanderen",
                "regionID": "BE25",
                "regionPopulation": 1177567 
            },
            {
                "regionName": "Prov. Brabant Wallon",
                "regionID": "BE31",
                "regionPopulation": 389479  
            },
            {
                "regionName": "Prov. Hainaut",
                "regionID": "BE32",
                "regionPopulation": 1332489 
            },
            {
                "regionName": "Prov. Liège",
                "regionID": "BE33",
                "regionPopulation": 1095977
            },
            {
                "regionName": "Prov. Luxembourg (BE)",
                "regionID": "BE34",
                "regionPopulation": 278278 
            },
            {
                "regionName": "Prov. Namur",
                "regionID": "BE35",
                "regionPopulation": 486069 
            }
        ]
    },
    {
        "countryName": "Bulgaria",
        "countryID": "BG",
        "countryPopulation": 7284552,
        "regions":[
            {
                "regionName": "Severozapaden",
                "regionID": "BG31",
                "regionPopulation": 823469 
            },
            {
                "regionName": "Severen tsentralen",
                "regionID": "BG32",
                "regionPopulation": 844511 
            },
            {
                "regionName": "Severoiztochen",
                "regionID": "BG33",
                "regionPopulation": 957460 
            },
            {
                "regionName": "Yugoiztochen",
                "regionID": "BG34",
                "regionPopulation": 1067981 
            },
            {
                "regionName": "Yugozapaden",
                "regionID": "BG41",
                "regionPopulation": 2128783 
            },
            {
                "regionName": "Yuzhen tsentralen",
                "regionID": "BG42",
                "regionPopulation": 1462348 
            }
        ]
    },
    ...

然后，我有两个变量： cs和rs 。 在任何时候，它们中只有一个不同于null。

cs包含用户选择的国家， rs包含用户选择的国家。 如前所述，如果cs与null不同，则rs为null，反之亦然。 这是因为用户可以从地图中选择国家或国家的区域。

我的目标是创建一个复选框（或类似的东西，我仍然要考虑一下），该复选框使您可以选择当前区域（国家）之外的其他区域（国家），以便您可以比较数据。

我想要的是：

• 如果cs != null >我想获取国家列表（Json文件中的所有国家）

• 如果rs != null >我想获取rs所属国家的地区列表。

互相了解：

这就是我试图做的。

// global variables
cs = null;  // if it is not null, the user has selected this country
csi = null; // country id
rs = null;  // if it is not null, the user has selected this region
rsi = null; // region id
currentCountries = null; // list of all countries
currentRegions = null; // list of regions in the selected country

/**
 * Function that creates line charts only when a country or a region is clicked.
 */
function createLineChart(antigenSelected, yearSelected, countrySelected, countrySelectedId, regionSelected, regionSelectedId) {
   defineLines(antigenSelected, yearSelected, countrySelected, countrySelectedId, regionSelected, regionSelectedId);
}

function defineLines(antigenSelected, yearSelected, countrySelected, countrySelectedId, regionSelected, regionSelectedId) {
   /**
    * To know if the user has clicked on the country or region, check that the selected region belongs to the selected country:
    *   - if it belongs to us -> the user has clicked on the selected region
    *   - if it does not belong to us -> the user has clicked on the selected country.
    * At any moment only one of the two possibilities is assigned (the other is null).
    */
   cs = null;  // if it is not null, the user has selected this country
   csi = null; // country id
   rs = null;  // if it is not null, the user has selected this region
   rsi = null; // region id

   // if the user has selected a region
   if(regionSelectedId != null && countrySelectedId == regionSelectedId.substring(0, 2)) {
      rs = regionSelected;
      rsi = regionSelectedId;
   }
   // if the user has selected a country
   else {
      cs = countrySelected;
      csi = countrySelectedId;
   }

   console.log("countrySelected: " + cs);
   console.log("regionSelected: " + rs);

   /**
    * Load json with countries and regions.
    */
   d3.json("../Project2/data/json/countriesAndRegions.json", function(error, countriesAndRegions) {
      if(error) {
         console.log("*** ERROR LOADING FILES: " + error + " ***");
         throw error;
      }

      countriesAndRegions.forEach(function(c) {
         allCountries.push(c.countryName);
         currentRegions = c.regions;
      });

      currentRegions.forEach(function(r) {
         //console.log(r.regionName);
      });

      console.log(allCountries);
      console.log(currentRegions);

      //var nested = d3.nest()
         // I have to nest data?
         //.object(currentRegions);

   });

}

显然，此代码不起作用。 或者说，它适用于allCountries但不适用于currentRegions 。 我该如何解决？ 我应该使用nest()方法吗？

我想要的是：

• 如果cs != null >获取所有国家
• 如果rs != null >获取rs区域所属国家的所有区域。

非常感谢

---

为了简化，假设我有这个json文件。

var users = [
    {
        name: 'Corbin',
        age: 20,
        favoriteFoods: ['ice cream', 'pizza'],
        other: [
            {
                a: 12,
                b: "apple"
            }, 
            {
                a: 15,
                b: "pear"
            }
        ]
    },
    {
        name: 'John',
        age: 25,
        favoriteFoods: ['ice cream', 'skittle'],
        other: [
            {
                a: 0,
                b: "cinnamon"
            }, 
            {
                a: 854,
                b: "ginger"
            }, 
            {
                a: 24,
                b: "salt"
            }
        ]
    }
];

然后我有一个包含字符串ginger的变量。 如何获得清单[cinnamon, ginger, salt] ？

如果我有一个包含字符串Corbin的变量，如何获取列表[Corbin, John] ？

Answer 1

例如我有一个与您的json数组相同的json数组示例：

var users = [{name: 'Corbin', age: 20, favoriteFoods: ['ice cream', 'pizza']},
             {name: 'John', age: 25, favoriteFoods: ['ice cream', 'skittle']}];

并且我必须访问第二个用户的age属性，然后： users[1].age将起作用。

如果必须访问第一个用户的第二个“ favoriteFood”，则应使用： users[0].favoriteFoods[2] 。

根据您的要求，我将发布另一个示例代码：

Answer 2

好的，此要求要求根据值来获取key ，并且我想出了一种使用递归调用的方法（不过可能有更好的方法）。

步骤（ 简化 ）：

1. 遍历数组。 让我们将array的元素称为row 。
2. 通过Object.keys(row)获取row键
3. 循环浏览该row所有键。
4. 如果row[key]是一个对象，只需找到与传递的value （主值-cs或rs ）匹配的适当的键/值对，然后返回关联的key 。 我已经使用了break语句，最后使用了基于关联key的array.map（） 。
5. 但是，如果row[key]是一个Array ，请使用递归调用并执行上述步骤。

希望这能解释代码。 如果您有任何疑问，请告诉我。 :)

 var data = [ { "countryName": "Austria", "countryID": "AT", "countryPopulation": 8451860, "regions":[ { "regionName": "Burgenland (AT)", "regionID": "AT11", "regionPopulation": 286691 }, { "regionName": "Niederösterreich", "regionID": "AT12", "regionPopulation": 1618592 }, { "regionName": "Wien", "regionID": "AT13", "regionPopulation": 1741246 }, { "regionName": "Kärnten", "regionID": "AT21", "regionPopulation": 555473 }, { "regionName": "Steiermark", "regionID": "AT22", "regionPopulation": 1210971 }, { "regionName": "Oberösterreich", "regionID": "AT31", "regionPopulation": 1418498 }, { "regionName": "Salzburg", "regionID": "AT32", "regionPopulation": 531898 }, { "regionName": "Tirol", "regionID": "AT33", "regionPopulation": 715888 }, { "regionName": "Vorarlberg", "regionID": "AT34", "regionPopulation": 372603 } ] }, { "countryName": "Belgium", "countryID": "BE", "countryPopulation": 11161642, "regions":[ { "regionName": "Région de Bruxelles-Capitale", "regionID": "BE10", "regionPopulation": 1174624 }, { "regionName": "Prov. Antwerpen", "regionID": "BE21", "regionPopulation": 1802309 }, { "regionName": "Prov. Limburg (BE)", "regionID": "BE22", "regionPopulation": 855963 }, { "regionName": "Prov. Oost-Vlaanderen", "regionID": "BE23", "regionPopulation": 1465150 }, { "regionName": "Prov. Vlaams-Brabant", "regionID": "BE24", "regionPopulation": 1103737 }, { "regionName": "Prov. West-Vlaanderen", "regionID": "BE25", "regionPopulation": 1177567 }, { "regionName": "Prov. Brabant Wallon", "regionID": "BE31", "regionPopulation": 389479 }, { "regionName": "Prov. Hainaut", "regionID": "BE32", "regionPopulation": 1332489 }, { "regionName": "Prov. Liège", "regionID": "BE33", "regionPopulation": 1095977 }, { "regionName": "Prov. Luxembourg (BE)", "regionID": "BE34", "regionPopulation": 278278 }, { "regionName": "Prov. Namur", "regionID": "BE35", "regionPopulation": 486069 } ] }, { "countryName": "Bulgaria", "countryID": "BG", "countryPopulation": 7284552, "regions":[ { "regionName": "Severozapaden", "regionID": "BG31", "regionPopulation": 823469 }, { "regionName": "Severen tsentralen", "regionID": "BG32", "regionPopulation": 844511 }, { "regionName": "Severoiztochen", "regionID": "BG33", "regionPopulation": 957460 }, { "regionName": "Yugoiztochen", "regionID": "BG34", "regionPopulation": 1067981 }, { "regionName": "Yugozapaden", "regionID": "BG41", "regionPopulation": 2128783 }, { "regionName": "Yuzhen tsentralen", "regionID": "BG42", "regionPopulation": 1462348 } ] } ]; var cs = 'Belgium', rs = 'Yuzhen tsentralen'; // cs is not null, get all countries but first find the key var mainKey = null; function getKey(array, value) { for(var i=0; i<array.length; i++) { var flag = false, row = array[i], keys = Object.keys(row); for(var j=0; j<keys.length; j++) { var key = keys[j]; if(Array.isArray(row[key])) { getKey(row[key], value); } else if(row[key] === value) { mainKey = key; flag = true; console.log(array.map(function(d) { return d[mainKey];})); break; } } if(flag) { break; } } } if(cs != null) { getKey(data, cs); } if(rs != null) { getKey(data, rs); } /******************** This is what I thought earlier about the requirement, use it if you find it helpful *************/ /* // with underscore.js var row = _.findWhere(data, {countryName: cs}); if(row) { console.log(row["regions"]); console.log(row["regions"].map(function(r) { return r["regionName"]; })); } // without underscore.js var index = null; for(var i=0; i<data.length; i++) { if(data[i]['countryName'] === cs) { index = i; break; } } console.log(data[index]["regions"]); console.log(data[index]["regions"].map(function(r) { return r["regionName"]; })); */ 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script> 

Answer 3

主要问题在这段代码中：

regionSelectedId != null && countrySelectedId == regionSelectedId.substring(0, 2)

由于当regionSelectedId为null时countrySelectedId将始终为null ，因此该表达式将始终返回false。 您只需要将其修改为有用的内容即可。