This is not a duplicate of Merging/Joining GeoJSON and JSON? because I need to join on client side.

I want to develop a choropleth map. I am using the same tutorial of Leaflet. I am also using the same statesData provided in that tutorial. The problem is value. I am getting an API which providing me the value of states. The 2nd JSON is providing me the id of states and its corresponding value. I want to visualize the choropleth map using these instead of Density value given in the statesData.js file.


How can I put this value to obtain a choropleth map instead of using density that showed in the tutorial?

  • Can you link an example complete JSON response from the API?
    – 15Step
    Commented Mar 27, 2018 at 11:08

2 Answers 2


Since GeoJSON is based on JSON, you are simply looking for joining two JSON objects. I think that this question is almost similar with yours and there are alternative solutions(pure js or using jQuery) .

  • GeoJSON is based on JSON but in GeoJSON feature collection that is a special format that can easily be read by different GIS libraries mainly Leaflet. I was stuck there. One is simply a JSON format and another is GeoJSON feature collection. Commented Mar 28, 2018 at 16:21
  • 1
    I think that looping over features of feature collection similar to the one of the answers at the link will solve the problem. I'll try to implement working code when I have access to a computer. Commented Mar 28, 2018 at 16:48
  • Here is a working example: jsfiddle.net/L9tamn7a/22 Commented Mar 29, 2018 at 8:51

Since there are not that many values the simplest solution would be to create lookup array for JSON data:

var array = [{"id":"01","value":130.36},{"id":"02","value":125.36},{"id":"03","value":525.36}];
var lookup = {};
for (var i = 0, len = array.length; i < len; i++) {
    lookup[array[i].id] = array[i];

Now you can get value for some lookup_id where you need it by simple object reference:

desired_value = lookup[lookup_id].value;

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