merge object & sum a single property javascript

Question

i have an array like this

[
  {
    item_guid: \"57e7a1cd6a3f3669dc03db58\"
    quantity:3
  },
  {
    item_guid: \"57e77b06e0566d496b51fed5\"
    quantity:         


        

Answer 1

You can

• group your objects by item_guid
• sum the objects in the resulting groups
• transform these groups in the format you want

Something like this:

var result = _.chain(data)
    .groupBy('item_guid')
    .map(function(objects, guid) {
        return {
            item_guid: guid, 
            quantity: _.sumBy(objects, 'quantity')
        };
    })
    .value();

And a demo

var data = [
  {
    item_guid: "57e7a1cd6a3f3669dc03db58",
    quantity:3
  },
  {
    item_guid: "57e77b06e0566d496b51fed5",
    quantity:3
  },
  {
    item_guid: "57e7a1cd6a3f3669dc03db58",
    quantity:3
   },
  {
    item_guid: "57e77b06e0566d496b51fed5",
    quantity:3
  }
];


var result = _.chain(data)
    .groupBy('item_guid')
    .map(function(objects, guid) {
        return {
            item_guid: guid, 
            quantity: _.sumBy(objects, 'quantity')
        };
    })
    .value();
  
  console.log(result);