Javascript reducing to the sum of an array of arrays of integers

Question

I have an array of arrays of integers that looks like this [[5, 3], [2,1], [4, 3]] and the output I am expecting is [8, 3, 7], but I seem to be missing something in my reduce function, as I'm getting an array of n undefined values like [undefined, undefined, undefined] since n=3

How can I get the sum of each array in the arrays and load that into an array?

const reducer = (accumulator, currentValue) => accumulator + currentValue;

const dayArray = [[3,5],[4,6],[8,2]];

const twoWeekArray = dayArray.map((day, index) => {
  return day.reduce(reducer);
});

console.log(twoWeekArray);

You don't return from the map's arrow function – Ori Drori Jan 22 '21 at 21:08 — Ori Drori, Jan 22 '21 at 21:08

score 1 · Accepted Answer · answered Jan 22 '21 at 21:11

1

You forgot to return:

dayArray = [[3,5],[4,6],[8,2]];
twoWeekArray = dayArray.map((day, index) => {
    return day.reduce(function (a, b) {
        return a + b;
    });
});

answered Jan 22 '21 at 21:11

Lior Pollak

3,362
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BTW You can also use arrow functions. In that case, you don’t need to return. – Lior Pollak Jan 22 '21 at 21:50

Jose Marin · Answer 2 · 2021-01-22T21:15:35.117

0

Here you go...

const subject = [[5, 3], [2,1], [4, 3]]

const result = 
  subject.map((elem) => 
    elem.reduce((acum, current) =>
      acum = acum + current,
      0
    )
   )
   

console.log(result)

edited Jan 22 '21 at 21:15

answered Jan 22 '21 at 21:09

Jose Marin

802
1
4
15

what if we dont know the number of values in each array? – IWI Jan 22 '21 at 21:10
I changed it to fit your new requirements. – Jose Marin Jan 22 '21 at 21:16

Javascript reducing to the sum of an array of arrays of integers

2 Answers2