Adding numbers inside array of arrays

Question

Here I'm trying to add number of array separately, but I'm not able to achieve the expected output. If I want to add total I would do flatMap and add them togeather. But I want add them separately for each array.

Below is the snippet for what I have tried

const data = [{
    "itemDetails": [{
      "sizeOfBag": 1,
      "numberOfBags": 1,
      "quantityInBag": 1.0
    }]
  },
  {

    "itemDetails": [{
        "sizeOfBag": 1,
        "numberOfBags": 1,
        "quantityInBag": 1.0
      },
      {
        "sizeOfBag": 10,
        "numberOfBags": 1,
        "quantityInBag": 1.0
      }
    ],

  }
]
const newData = data.map(f => f.itemDetails);
console.log(newData);

for (let i = 0; i <= newData.length; i++) {
  const addData = newData.reduce((acc, newData) => acc + newData[i].sizeOfBag, 0);
}
console.log(addData);

Expected Output: [1,11]

You have the for loop syntax wrong, it should be ; between the parts of the header, not ,. — Barmar
– Barmar, Commented Jul 9, 2020 at 5:41

Unmitigated · Accepted Answer · 2020-07-09 05:48:13Z

1

You can use map and reduce.

const res = newData.map(arr=>arr.reduce((acc,curr)=>acc+curr.sizeOfBag,0));

Your attempt with the for loop is close, but you are looping past the last index and mixing up your index with property names.

for (let i = 0; i < newData.length; i++) {
  newData[i] = newData[i].reduce((acc, newData) => acc + newData.sizeOfBag, 0);
}

edited Jul 9, 2020 at 5:48

answered Jul 9, 2020 at 5:43

Unmitigated

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4 Comments

Teja Over a year ago

One doubt here. We are using map twice, so why can't we use flatMap ?

Unmitigated Over a year ago

We are only using map once. The result is a one dimensional array so there is no need to flatten it.

Teja Over a year ago

is it possible to get the output as same [{"itemDetails": [{'totalSizeOfBag': 0}]},{"itemDetails": [{'totalSizeOfBag': 11}]}]

Unmitigated Over a year ago

I think that merits a new question.

Barmar · Accepted Answer · 2020-07-09 05:45:07Z

1

You need to call reduce on the nested arrays, not the top-level newData array. You can combine all these calls using map to get an array of the results.

const data = [{
    "itemDetails": [{
      "sizeOfBag": 1,
      "numberOfBags": 1,
      "quantityInBag": 1.0
    }]
  },
  {

    "itemDetails": [{
        "sizeOfBag": 1,
        "numberOfBags": 1,
        "quantityInBag": 1.0
      },
      {
        "sizeOfBag": 10,
        "numberOfBags": 1,
        "quantityInBag": 1.0
      }
    ],

  }
]
const newData = data.map(f => f.itemDetails);
console.log(newData);

const addData = newData.map(d => d.reduce((acc, x) => acc + x.sizeOfBag, 0));

console.log(addData);

answered Jul 9, 2020 at 5:45

Barmar

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1 Comment

Teja Over a year ago

is it possible to get the output as same [{"itemDetails": [{'totalSizeOfBag': 0}]},{"itemDetails": [{'totalSizeOfBag': 11}]}]

Ray Caballero · Accepted Answer · 2020-07-09 05:45:46Z

1

Do it like this, run the reduce function inside your map:

data.map(f => f.itemDetails.reduce((acc, i) => acc + i.sizeOfBag, 0));

answered Jul 9, 2020 at 5:45

Ray Caballero

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3 Comments

Teja Over a year ago

is it possible to get the output as same [{"itemDetails": [{'totalSizeOfBag': 0}]},{"itemDetails": [{'totalSizeOfBag': 11}]}]

Barmar Over a year ago

Yes, it's possible. But that's not what you said you wanted as expected output.

Barmar Over a year ago

Use {totalSizeOfBag: 0} as the 2nd argument to reduce, and (acc.totalSizeOfBag += i.sizeOfBag, acc) as the body of the arrow function.

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