How to add all numerical key-values in array of objects?

Question

If you have an array of objects like so:

What's the best way to add all numerical values in each object so each one looks something like this:

{category: "A", total: 44}

So in the 0th item in the original array, 0+23+21 is 24, and is now represented by the new 'total' key.

Bearing in mind that the 'keys' with numerical values in the original array e.g. 'col2' are randomly generated (so another array like the original can have keys like 'somethingelse'.

I've attempted it with the following, but I believe it's not written correctly:

newArrayOfObjects.forEach(element => {
    Object.values(element).reduce((a, b) => a + b);
});

It may be good to know but the 'key' category always exists in each object and is fixed. All other key values are numerical and there'll always be more than one.

Images are OK but isn't mandatory but code as a minimal reproducible example is required 99% of the time. — zer00ne
– zer00ne, Commented Jun 20, 2022 at 9:51
const results = newArrayOfObjects.map(element => Object.values(element).reduce((sum,value) => typeof value === 'number' ? sum+value : sum, 0)) — Ouroborus
– Ouroborus, Commented Jun 20, 2022 at 9:52

Mina · Accepted Answer · 2022-06-20 09:51:21Z

4

Please check this.

const array = [
  {
    category: 'A',
    col1: 1,
    col2: 2,
    col3: 3,
  },
  {
    category: 'B',
    col1: 2,
    col2: 3,
    col3: 4,
  }
]

const result = array.map(obj => {
  const total = Object.values(obj).reduce((acc, value) => {
    if (typeof value === 'number') {
      return acc + value;
    }
    return acc;
  }, 0)
  return {
    category: obj.category,
    total
  }
})

console.log(result)

answered Jun 20, 2022 at 9:51

Mina

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2 Comments

frankie303 Over a year ago

it could be solved with O(n) complexity (please see my solution below), no need to have O(n^2).

Mina Over a year ago

But in your example, you restrict the numeric value keys to col2 and col3, but @One_for_all said that key can be any value, so I'm sorry your answer isn't valid.

Terry Lennox · Accepted Answer · 2022-06-20 09:54:32Z

You could use Array.map() along with Array.reduce() to sum the numeric values in the array.

We'd create a toNumber() function to get the numeric value of any property. If this is not a number, it will return 0 (keeping the total unchanged).

let arr = [
   { a: 0, category: "a", col2: 23, col3: 21 },
   { b: 0, category: "b", x: 100, y: 10, z: 1 },
   { j: 0, category: "x", foo: 25, bar: 50, meta: 'content' },
]

function toNumber(n) {
    return isNaN(n) ? 0: n;
}

function sumTotals(a) {
    return a.map(({ category, ...obj}) => {
        const total = Object.values(obj).reduce((total, value) => { 
            return total + toNumber(value); 
        }, 0);
        return { category, total };
    })
}

console.log('Totals:', sumTotals(arr))

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

rıza meydan · Accepted Answer · 2022-06-20 09:54:35Z

0

arr = [{x:1}, {x:3}]

arr.reduce((accumulator, current) => accumulator + current.x, 0);

answered Jun 20, 2022 at 9:54

rıza meydan

1

1 Comment

Community Over a year ago

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nsevens · Accepted Answer · 2022-06-20 09:55:06Z

0

var data = [
    { "category": "A", "col0": 5, "col1": 8, "some": "thing"},
    { "category": "B", "col1": 3, "col2": 5}
];

var res = data.map((it) => {
    const { category, ...rest } = it;
    return {
      ...it,
      total: Object.values(rest).reduce(
        (prev, curr) =>
          typeof curr === "number" ? prev + curr : prev, // add if the current value is numeric
          0
      )
    }
});

console.log(res);

/**
[
  {"category":"A","col0":5,"col1":8,"some":"tst","total":13}, 
  {"category":"B","col1":3,"col2":5,"total":8}
]
**/

answered Jun 20, 2022 at 9:55

nsevens

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Comments

Steffen Frank · Accepted Answer · 2022-06-20 09:58:15Z

0

I think you are on the right way, you just need to do a bit more destructuring and type checking:

const aggregated = newArrayOfObjects.map((obj) =>
  Object.entries(obj).reduce(
    (newObj, [key, value]) => ({
      ...newObj,
      ...(typeof value === "number"
        ? { total: newObj.total + value }
        : { [key]: value }),
    }),
    { total: 0 }
  )
);

First, you map all objects to their representations as key-value-pairs. Then you iterate over these key-value pairs and keep all non-numerical values and their respective keys, while dropping key-value-pairs with a numerical value and replacing them by a property in which you aggregate the total value.

answered Jun 20, 2022 at 9:58

Steffen Frank

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