I want to reduce only a specific position in a nested number array
const array1 = [[1,2,3],[4,5,6],[7,8,9],[11,12,13]];
console.log(array1.reduce((prev, curr) => prev[2] + curr[2]));
The result is NaN, another solution?
1) You should use prev not prev[2] as
prev is of type number that you are returning not an array
2) If you are adding the number then it is better to take initial value as 0 as a second argument to the reduce method.
If you won't pass second argument, then reduce will take the array element at 0 index as the starting value i.e [1, 2, 3] and then if you add [1, 2, 3] + curr[2] then it will produce value as 1,2,36, which you are not expecting
const array1 = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9],
[11, 12, 13],
];
console.log(array1.reduce((prev, curr) => prev + curr[2], 0));