how to sum arrays of array?

Question

I know we can sum the array elements using reduce() but what if we have an array of arrays. For eg:

var result=[10,20,30];
result.reduce((a, b) => a + b)

it will return 60

but if we have

result=[
  [10,20,30],
  [20,30,40],
  [60,70,80]
]
console.log(result);

how can we get the final result as result=[60,90,210] using reduce?

It seems to me that you want to mutate the result array. In that case, do: result.forEach(function(d, i, arr) { arr[i] = d.reduce((a, b) => a + b, 0);}); — Gerardo Furtado
– Gerardo Furtado, Commented Sep 23, 2019 at 3:36

Jaisa Ram · Accepted Answer · 2019-09-23 03:20:11Z

5

fisrt you can map and inside map use reduce

result=[
  [10,20,30],
  [20,30,40],
  [60,70,80]
  ]
const final = result.map(item => item.reduce((a, b)=> a + b, 0))

console.log(final)

edited Sep 23, 2019 at 3:20

answered Sep 23, 2019 at 3:14

Jaisa Ram

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Comments

Nithin Kumar Biliya · Accepted Answer · 2019-09-23 03:36:06Z

1

You can use Array.prototype.map() to loop through each of the subarrays in the outer array. The map() method creates a new array with the results of calling a provided function on every element in the calling array.

Once you get a subarray, follow the previous approach to find the sum using reduce().

result = result.map(subArray => subArray.reduce((a, b) => a + b))

answered Sep 23, 2019 at 3:36

Nithin Kumar Biliya

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Comments

sinnerwithguts · Accepted Answer · 2019-09-25 09:55:18Z

0

If you want to use .reduce only, I suggest this code:

 result=[
  [10,20,30],
  [20,30,40],
  [60,70,80]
]
const sum = result.reduce((a, b) => {
  return [...a.concat(b.reduce((a, b) => a + b, 0))]
}, [])
console.log(sum)

answered Sep 25, 2019 at 9:55

sinnerwithguts

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