How to calculate sum of array in JavaScript

Question

I want to calculate sum of array data in JavaScript.

Array :

[
  {
    red_team: {
      count: 2,
      money: 3000,
    },
    blue_team: {
      count: 10,
      money: 100000,
    },
  },
  {
    red_team: {
      count: 1,
      money: 1000,
    },
    blue_team: {
      count: 100,
      money: 200000,
    },
  }
]

Expected Result :

{
  red_team: {
    count: 3,
    money: 4000,
  },
  blue_team: {
    count: 110,
    money: 300000,
  },
}

Note : red_team & blue_team is an Enum.

how can I calculate it ?

There are many ways to do this. But first you should attempt to figure it out yourself. That is the best way to learn. Start out by looping through the array and keep a value for red_team and a value for blue_team — J. Cutshall
– J. Cutshall, Commented Feb 28, 2022 at 18:08
Do you know the amount of objects there are in the array (e.g. since this is a game, do you know the amount of rounds beforehand)? — ethry
– ethry, Commented Mar 1, 2022 at 7:31

Ori Drori · Accepted Answer · 2022-02-28 18:31:54Z

3

Spread the array into lodash's _.mergeWith(), and create a customizer that sums number, but returns undefined for all other types, so that lodash would handle all other cases:

const data = [{"red_team":{"count":2,"money":3000},"blue_team":{"count":10,"money":100000}},{"red_team":{"count":1,"money":1000},"blue_team":{"count":100,"money":200000}}]


const result = _.mergeWith({}, ...data, (a, b) => 
  _.isNumber(a) ? a + b : undefined
)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

answered Feb 28, 2022 at 18:31

Ori Drori

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Comments

Riza Khan · Accepted Answer · 2022-02-28 18:28:54Z

Per a comment above, an infinite ways of doing this. I just came up with one (rather verbose admittedly)

Verbose solution:

const arr = [
  {
    red_team: {
      count: 2,
      money: 3000,
    },
    blue_team: {
      count: 10,
      money: 100000,
    },
  },
  {
    red_team: {
      count: 1,
      money: 1000,
    },
    blue_team: {
      count: 100,
      money: 200000,
    },
  }
];

function sumByKeyAndProperty(arr, key, property){
  let sum = 0
  arr.forEach((obj) => {
    sum+=obj[key][property]
  })
  return sum
}

returnObj = {
  red_team: {
    count: sumByKeyAndProperty(arr, 'red_team', 'count'),
    money: sumByKeyAndProperty(arr, 'red_team', 'money'),
  },
  blue_team: {
    count: sumByKeyAndProperty(arr, 'blue_team', 'count'),
    money: sumByKeyAndProperty(arr, 'blue_team', 'money'),
  }
}

console.log(returnObj)

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