Recursion - Sum Nested Array

Question

I\'m trying to sum a nested array [1,2,[3,4],[],[5]] without using loops but I don\'t see what\'s wrong with what I have so far.

function sumItem         


        

Answer 1

You may do as follows;

var sumNested = ([a,...as]) => (as.length && sumNested(as)) + (Array.isArray(a) ? sumNested(a) : a || 0);

console.log(sumNested([1,2,3,[4,[5,[6]]],7,[]]));

The function argument designation [a,…as] means that when the function is fed with a nested array like [1,2,3,[4,[5,[6]]],7,[]] then a is assigned to the head which is 1 and as is assigned to the tail of the initial array which is [2,3,[4,[5,[6]]],7,[]]. The rest should be easy to understand.

Answer 2

function arraySum (array) {
  if (array.length > 0) {
    return arraySum(array[0]) + arraySum(array.slice(1));
  }
  if (array.length === 0) {
    return 0;
  } else {
    return array;
  }
};

Answer 3

Here's a version without using loops:

function f(arr, i){
  if (i == arr.length)
    return 0;
	
  if (Array.isArray(arr[i]))
    return f(arr[i], 0) + f(arr, i + 1);
	  
  return arr[i] + f(arr, i + 1);
}

console.log(f([1,2,[3,4],[],[5]], 0));

Answer 4

try with

 function sumItems(array) {

  let sum = 0;
  array.forEach((item) => {
    if(Array.isArray(item)) {
     sum += sumItems(item);
    } else {
    sum += item;
    }
  })
  return sum;
}

Answer 5

This is similar to some of the other solutions but might be easier for some to read:

 function Sum(arr) {
   if (!arr.length) return 0;
   if (Array.isArray(arr[0])) return Sum(arr[0]) + Sum(arr.slice(1));
   return arr[0] + Sum(arr.slice(1));
 }

 console.log(Sum([[1],2,[3,[4,[5,[6,[7,[8,9,10],11,[12]]]]]]])) // 78

Answer 6

You could define a callback for using with Array#reduce, which check if an item is an array and uses this function again for that array.

function add(s, v) {
    return Array.isArray(v)
        ? v.reduce(add, s)
        : s + v;
}

var array = [1, 2, [3, 4], [], [5]];

console.log(array.reduce(add, 0));