Creating key value pairs from json on import

Question

I am new to jquery - I have a valid geojson file whose features I would like to access and convert into an object of key-value pairs. My objective is to only use properties.cat as the key and properties.name as the value (all other data can be ignored). Here is a sample:

{
"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);

      });

As was pointed out below, features is an array. How could one create an object of key value pairs directly from every feature property in the json so as to have the following output:

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

Did you try logging the json variable to the console prior to parsing it? — Botimoo, Jun 04 '17 at 19:22

Mihai Alexandru-Ionut · Accepted Answer · 2017-06-04T20:40:03.683

1

The callback function for $.getJson method has response already parsed automatically.

Also, features object is an array. Use this:

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

For making key-value pairs you can use reduce method, which accepts a callback provided method applied for every item.

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);

edited Jun 04 '17 at 20:40

answered Jun 04 '17 at 19:21

Mihai Alexandru-Ionut

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Thanks, I've edited my question – iskandarblue Jun 04 '17 at 19:30
@the_darkside, have a look to updated answer. – Mihai Alexandru-Ionut Jun 04 '17 at 20:01
thanks @Alexandru but when I wrap that in getJSON it does not work: `$.getJSON("sample.geojson", function(json) { var obj={}; json.features.reduce(function(obj,item){ obj[item.properties.cat]=item.properties.name; return obj; },{}); console.log(obj) });` – iskandarblue Jun 04 '17 at 20:27
why does this work within the getJSON function? – iskandarblue Jun 04 '17 at 20:28
It's because console.log is execute before the callback reduce is finished – Mihai Alexandru-Ionut Jun 04 '17 at 20:39
Have a look to my answer. – Mihai Alexandru-Ionut Jun 04 '17 at 20:40
Your answer works, but it does not take into account that I have to read in the json from a file first. I need to use `getJSON` because My actual json file is much larger and I cannot include it in the script. Does that make sense? – iskandarblue Jun 04 '17 at 20:43
Do you use node.js like server-side ? – Mihai Alexandru-Ionut Jun 04 '17 at 20:44
Like you posted the question , I suppose that the part which read from file is working good. – Mihai Alexandru-Ionut Jun 04 '17 at 20:45
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/145822/discussion-between-the-darkside-and-alexandru-ionut-mihai). – iskandarblue Jun 04 '17 at 20:46

Creating key value pairs from json on import

1 Answers1