在导入时从 json 创建键值对 [重复]

Question

我是 jquery 的新手 - 我有一个有效的 geojson 文件，我想访问其 features 并将其转换为键值对对象。我的目标是只使用properties.cat 作为键和properties.name 作为值（可以忽略所有其他数据）。这是一个示例：

{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:EPSG::3857" } },
"features": [
{ "type": "Feature", "properties": { "cat": "A", "name": "Aberdeen"}, "geometry": { "type": "Point", "coordinates": [ 16.37208, 48.20849 ] } },
{ "type": "Feature", "properties": { "cat": "B", "name": "Berlin"}, "geometry": { "type": "Point", "coordinates": [ 4.3517103, 50.8503396 ] } },
{ "type": "Feature", "properties": { "cat": "C", "name": "Copenhagen"}, "geometry": { "type": "Point", "coordinates": [ 4.3517103, 50.8503396 ] } },
{ "type": "Feature", "properties": { "cat": "D", "name": "Dublin" }, "geometry": { "type": "Point", "coordinates": [ 12.56553, 55.67594 ] } },
{ "type": "Feature", "properties": { "cat": "E", "name": "Edinburgh"}, "geometry": { "type": "Point", "coordinates": [ -3.7037902, 40.4167754 ] } }
]
}


  $.getJSON("sample.geojson", function(json) {

    console.log(json.features[0].properties.cat);

      });

正如下面指出的，features 是一个数组。 如何直接从 json 中的每个特征属性创建一个键值对对象，从而获得以下输出：

{A : Aberdeen, B: Berlin, C: Copenhagen, D: Dublin, E: Edinburgh}

Answer 1

$.getJson 方法的回调函数已经自动解析了响应。

另外，features 对象是一个数组。使用这个：

console.log(json.features[0].properties.cat);

您可以使用reduce 方法制作键值对，该方法接受callback 提供的方法应用于每个项目。

var json= {
      "type": "FeatureCollection",
      "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:EPSG::3857" } },
      "features": [
      { "type": "Feature", "properties": { "cat": "A", "name": "Aberdeen"}, "geometry": { "type": "Point", "coordinates": [ 16.37208, 48.20849 ] } },
      { "type": "Feature", "properties": { "cat": "B", "name": "Berlin"}, "geometry": { "type": "Point", "coordinates": [ 4.3517103, 50.8503396 ] } },
      { "type": "Feature", "properties": { "cat": "C", "name": "Copenhagen"}, "geometry": { "type": "Point", "coordinates": [ 4.3517103, 50.8503396 ] } },
      { "type": "Feature", "properties": { "cat": "D", "name": "Dublin" }, "geometry": { "type": "Point", "coordinates": [ 12.56553, 55.67594 ] } },
      { "type": "Feature", "properties": { "cat": "E", "name": "Edinburgh"}, "geometry": { "type": "Point", "coordinates": [ -3.7037902, 40.4167754 ] } }
      ]
}
var obj=json.features.reduce(function(obj,item){
  obj[item.properties.cat]=item.properties.name;
  return obj;
},{});
console.log(obj);