merge object & sum a single property javascript

Question

i have an array like this

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

What i want from this to merge similar item_guid into one object and quantity get summed up like this

[
  {
    item_guid: "57e7a1cd6a3f3669dc03db58"
    quantity:6
   },
  {
    item_guid: "57e77b06e0566d496b51fed5"
    quantity:6
  }
]

I know this can be achieved some loop, instead I'm looking for solutions that uses lodash or EcmaScript2015 code to make our life easier

my suggestion is use Linq.js rather than writing custom method for achieve this linqjs.codeplex.com — Shobhit Walia
– Shobhit Walia, Commented Oct 26, 2016 at 12:35

Rajesh Dixit · Accepted Answer · 2019-09-27 07:47:44Z

5

A simple approach:

Loop over data and create an object where key will be unique id and its value will be quantity. Then loop back over object's keys and create objects.

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

var r = {};
data.forEach(function(o){
  r[o.item_guid] = (r[o.item_guid] || 0) + o.quantity;
})

var result = Object.keys(r).map(function(k){
  return { item_guid: k, quantity: r[k] }
});
console.log(result)

edited Sep 27, 2019 at 7:47

answered Oct 26, 2016 at 12:44

Rajesh Dixit

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Comments

Nina Scholz · Accepted Answer · 2016-10-26 13:15:08Z

A solution in plain Javascript with a hash table for item_guid.

var data = [{ item_guid: "57e7a1cd6a3f3669dc03db58", quantity: 3 }, { item_guid: "57e77b06e0566d496b51fed5", quantity: 3 }, { item_guid: "57e7a1cd6a3f3669dc03db58", quantity: 3 }, { item_guid: "57e77b06e0566d496b51fed5", quantity: 3 }],
    grouped = data.reduce(function (hash) {
        return function (r, a) {
            (hash[a.item_guid] = hash[a.item_guid] || r[r.push({ item_guid: a.item_guid, quantity: 0 }) - 1]).quantity += a.quantity;
            return r;
        };
    }(Object.create(null)), []);

console.log(grouped);

ES6

var data = [{ item_guid: "57e7a1cd6a3f3669dc03db58", quantity: 3 }, { item_guid: "57e77b06e0566d496b51fed5", quantity: 3 }, { item_guid: "57e7a1cd6a3f3669dc03db58", quantity: 3 }, { item_guid: "57e77b06e0566d496b51fed5", quantity: 3 }],
    grouped = data.reduce((map => (r, a) => {
        map.set(a.item_guid, map.get(a.item_guid) || r[r.push({ item_guid: a.item_guid, quantity: 0 }) - 1]);
        map.get(a.item_guid).quantity += a.quantity;
        return r;
    })(new Map), []);

console.log(grouped);

nikoshr · Accepted Answer · 2016-10-27 16:22:35Z

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);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js"></script>

chanoto89 · Accepted Answer · 2016-10-26 13:25:51Z

0

var groupedItems = [];

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

totalItems.forEach((e) => {
  if (groupedItems.findIndex(x => x.item_guid === e.item_guid) < 0) {
    let totalQuantity = totalItems
                       .filter(x => x.item_guid === e.item_guid)
                       .map(x => x.quantity)
                       .reduce(function(a, b) { return a + b;});

    groupedItems.push({item_guid: e.item_guid, quantity: totalQuantity})
  }
})

console.log(groupedItems);

answered Oct 26, 2016 at 13:25

chanoto89

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