Merging Objects In Array Based On Sub-value

I have an array populated with objects. How do I go about merging objects inside this array when they have a matching specific sub value? My array looks like this: var data = [

Solution 1:

What I do in example bellow., first I create object to achieve unique values (by project_id), and then converted object to array. In first loop I check if item does not exists in res - put to res, else I change only property type

var res = {};

$.each(data, function (key, value) {
    if (!res[value.product_id]) {
        res[value.product_id] = value;    
    } else {
        res[value.product_id].type = [
          res[value.product_id].type, 
          value.type
        ].join(',');
    }
});

data = $.map(res, function (value) {
  return value;
}); 

console.log(data);

Example