Merge Objects With The Same Id But Sum Values Of The Objects

I want to reduce my array of objects by comparing previous and current object from the array, if the id of previous object is different then current object, then I write the previo

Solution 1:

You can use thisArg parameter in forEach loop and pass a empty object to store values.

var data = [{"Clicks":210,"Company":"A","_id":{"CompanyID":5}},{"Clicks":35,"Company":"C","_id":{"CompanyID":3}},{"Clicks":15,"Company":"B","_id":{"CompanyID":2}},{"Clicks":13,"Company":"A","_id":{"CompanyID":5}}];
var result = [];

data.forEach(function(obj) {
  var id = obj._id.CompanyIDif(!this[id]) result.push(this[id] = obj);
  elsethis[id].Clicks += obj.Clicks;
}, Object.create(null));

console.log(result);

Solution 2:

For a version with Array#reduce, you could use a hash table as reference to the same company with a closure over the hash table.

var data = [{ Clicks: 210, Company: "A", _id: { CompanyID: 5 } }, { Clicks: 35, Company: "C", _id: { CompanyID: 3 } }, { Clicks: 15, Company: "B", _id: { CompanyID: 2 } }, { Clicks: 13, Company: "A", _id: { CompanyID: 5 } }],
    result = data.reduce(function (hash) {
        returnfunction (r, a) {
            var key = a._id.CompanyID;
            if (!hash[key]) {
                hash[key] = { Clicks: 0, Company: a.Company, _id: a._id };
                r.push(hash[key]);
            }
            hash[key].Clicks += a.Clicks;
            return r;
        };
    }(Object.create(null)), []);

console.log(result);

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