JavaScript reduce inner array of array and create answer array

Question

Array of arrays:

list = [[1, 2, 3], [4, 5, 6]];

I want to reduce (combine) each inner array (1+2+3) and (4+5+6) and then put those results 6 and 15 in their own array like [6, 15].

I have below code:

list.reduce((a, b) => a + b);

but it's just strangely combining everything in all the arrays.

Answer 1

You need to iterate both the outer and the inner arrays.

list.map(array => array.reduce((a, b) => a + b))

Answer 2

Use .map() with .reduce():

let list = [[1, 2, 3], [4, 5, 6]];
let reducer = (a, b) => (a + b);
let result = list.map(arr => arr.reduce(reducer));
console.log(result);

Answer 3

You can do it like this

map() with map we iterate on every element of arr.

reduce() - with reduce we reduce each element to a single value.

let arr = [[1,2,3],[4,5,6]];
let op = arr.map(e => e.reduce( (a, b) => a + b, 0) );
console.log(op);

Answer 4

You can also achieve this with Array.from since its second parameter is Array.map function and inside you can do your Array.reduce for the summation:

const data = [[1, 2, 3], [4, 5, 6]]
const result = Array.from(data, x => x.reduce((r,c) => r+c))
console.log(result)