How to group or merge this array of objects in javascript?

Question

I have an array of objects like below for example.

{name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0}
{name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0}
{name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0}
{name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1}
{name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1}
{name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0}
{name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1}
{name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1}

I want to group them up and adding up all the values in it. For example, the final would be like this:

{name: "Mc Donald", quantity: 8, maleCount: 1, femaleCount: 1}
{name: "KFC", quantity: 54, maleCount: 3, femaleCount: 3}

How can I achieve this in JavaScript?

I have tried to find some solution online but it is not the one I wanted. For example this solution

Faly · Accepted Answer · 2017-10-10 10:21:23Z

15

You can use array reduce:

var arr = [
    {name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0},
    {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
    {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
    {name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1},
    {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
    {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
    {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
    {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1}
];

var finalArr = arr.reduce((m, o) => {
    var found = m.find(p => p.name === o.name);
    if (found) {
        found.quantity += o.quantity;
        found.maleCount += o.maleCount;
        found.femaleCount += o.femaleCount;
    } else {
        m.push(o);
    }
    return m;
}, []);

console.log(finalArr);

answered Oct 10, 2017 at 10:21

Faly

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1 Comment

Prestaul Over a year ago

Just noting that this solution will modify some of the original objects.

Nenad Vracar · Accepted Answer · 2017-10-10 13:05:56Z

8

You can use forEach() loop and add to new array. You can pass empty object as thisArg parameter that you can use as this in your callback function and in second forEach context of this will still be the same as in first callback function because of arrow function.

var data = [{"name":"Mc Donald","quantity":4,"maleCount":1,"femaleCount":0},{"name":"KFC","quantity":9,"maleCount":1,"femaleCount":0},{"name":"KFC","quantity":9,"maleCount":1,"femaleCount":0},{"name":"Mc Donald","quantity":4,"maleCount":0,"femaleCount":1},{"name":"KFC","quantity":9,"maleCount":0,"femaleCount":1},{"name":"KFC","quantity":9,"maleCount":1,"femaleCount":0},{"name":"KFC","quantity":9,"maleCount":0,"femaleCount":1},{"name":"KFC","quantity":9,"maleCount":0,"femaleCount":1}]
var result = [], keys = ['quantity', 'maleCount', 'femaleCount']

data.forEach(function(e) {
  if(!this[e.name]) result.push(this[e.name] = e);
  else keys.forEach(k => this[e.name][k] += e[k])
}, {})

console.log(result)

edited Oct 10, 2017 at 13:05

answered Oct 10, 2017 at 10:22

Nenad Vracar

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1 Comment

Bergi Over a year ago

Using this like that needs some more explanation, please.

Nina Scholz · Accepted Answer · 2017-10-10 11:10:58Z

7

You could group with a hash table and use an array for the keys with variable values.

var array = [{ name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0 }, { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 }, { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 }, { name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1 }, { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 }, { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 }, { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 }, { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 }],
    groups = Object.create(null),
    result = array.reduce(function (r, o) {
        var values = ['quantity', 'maleCount', 'femaleCount'];
        if (!groups[o.name]) {
            groups[o.name] = { name: o.name };
            r.push(groups[o.name]);
            values.forEach(function (k) { groups[o.name][k] = 0; });
        }
        values.forEach(function (k) { groups[o.name][k] += o[k]; });
        return r;
    }, []);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

With linq.js

var array = [{ name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0 }, { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 }, { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 }, { name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1 }, { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 }, { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 }, { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 }, { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 }],
    result = Enumerable.From(array)
        .GroupBy(
            "$.name",
            null,
            "{ name: $.Key, quantity: $$.Sum('$.quantity'), maleCount: $$.Sum('$.maleCount'), femaleCount: $$.Sum('$.femaleCount') }"
        )
        .ToArray();

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/linq.js/2.2.0.2/linq.js"></script>

edited Oct 10, 2017 at 11:10

answered Oct 10, 2017 at 10:22

Nina Scholz

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2 Comments

Rick Hitchcock Over a year ago

Is there a reason to do groups = Object.create(null) instead of simply groups = {}?

Nina Scholz Over a year ago

if you have a name like toString, you could get wrong results with prototypes.

Apolo · Accepted Answer · 2017-10-10 12:29:48Z

My solution based on reduce:

let data = [
  {name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0},
  {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
  {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
  {name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1},
  {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
  {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
  {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
  {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1}
];

// We will only keep an array of values of the merged object
let result = Object.values(
  // Merge data to name indexed objects
  data.reduce((p,c) => {
    // Ensure key (name) exists
    if (!p[c.name]) {
       // If first occurence, duplicate object (to avoid modification of original array)
       p[c.name] = Object.assign({}, c);
    } else {
       // If key (name) already exists, sum up relevant attributes
       p[c.name].quantity += c.quantity;
       p[c.name].maleCount += c.maleCount;
       p[c.name].femaleCount += c.femaleCount;
    }
    // return updated object
    return p;
  }, {})
);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

hope this will help

grzesiekgs · Accepted Answer · 2017-10-10 10:28:39Z

More functional/universal approach

const normalizeValue = (value) => value === undefined ? 0 : value
const sumUpProps = (props = []) => (a = {}, b = {}) => {
  const result = {}
  
  props.forEach((prop) => {
    result[prop] = normalizeValue(a[prop]) + normalizeValue(b[prop])
  })

  return result
}

const data = [
  {name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0},
  {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
  {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
  {name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1},
  {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
  {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
  {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
  {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1}
]

const entries = {}
const sumObjects = sumUpProps(['quantity', 'maleCount', 'femaleCount'])

data.forEach((item) => {
  const entry = entries[item.name] || {}

  entries[item.name] = sumObjects(entry, item)
})


console.log(entries)

N-Alpr · Accepted Answer · 2017-10-10 10:33:38Z

check this code below:

var array = [
    {name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0},
    {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
    {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
    {name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1},
    {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
    {name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0},
    {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
    {name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1},
];

var result = [];

for(var index in array){
    var obj = array[index];
    if(result.hasOwnProperty(obj.name)) {
        result[obj.name].quantity += obj.quantity;
        result[obj.name].maleCount += obj.maleCount;
        result[obj.name].femaleCount += obj.femaleCount;
    }else{
        result[obj.name] = {};
        result[obj.name].quantity = obj.quantity;
        result[obj.name].maleCount = obj.maleCount;
        result[obj.name].femaleCount = obj.femaleCount;
    }
}

console.log(result);

ValarDohaeris-fuck-OpenAI · Accepted Answer · 2017-10-10 12:09:24Z

Here is a generic solution that uses clean and modern JavaScript:

function groupRestaurants(restaurants) {
    const groups = new Map();
    restaurants.forEach(restaurant => {
        const group = findOrCreateGroup(groups, restaurant.name);
        addRestaurantToGroup(group, restaurant);
    });
    return [...groups.values()];
}

function findOrCreateGroup(groups, name) {
    let group = groups.get(name);
    if (!group) {
        group = { name };
        groups.set(name, group);
    }
    return group;
}

function addRestaurantToGroup(group, restaurant) {
    for (const [key, value] of Object.entries(restaurant)) {
        if (key !== 'name') {
            if (group.hasOwnProperty(key)) {
                group[key] += value;
            } else {
                group[key] = value;
            }
        }
    }
}

const restaurants = [
    { name: "Mc Donald", quantity: 4, maleCount: 1, femaleCount: 0 },
    { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 },
    { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 },
    { name: "Mc Donald", quantity: 4, maleCount: 0, femaleCount: 1 },
    { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 },
    { name: "KFC", quantity: 9, maleCount: 1, femaleCount: 0 },
    { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 },
    { name: "KFC", quantity: 9, maleCount: 0, femaleCount: 1 }
];

console.log(groupRestaurants(restaurants));

dun · Accepted Answer · 2017-10-10 15:46:12Z

1

Lodash makes your life easy.

_.map(_.groupBy(yourArrayHere, 'name'), (groupMembers, groupKey) => {
    let sumObject = {name: groupKey};

    _.forEach(['quantity', 'maleCount', 'femaleCount'], (property) => {
        sumObject[property] = 0;
        _.forEach(groupMembers, (member) => {
            sumObject[property] += member[property];
        });
    });

    return sumObject;
});

answered Oct 10, 2017 at 15:46

dun

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