Sum JavaScript multidimensional array recursively

Question

I want to sum the total of a multi dimensional array in JavaScript however it doesn't provide the right value because the nested array concatenates with the sum. Below is my code:

    var arr = [1, 2, 3, [4, 3], [10, 50], 98, 100];

    function recursion(array, length = 0) {
        if (array.length === length) return 0;

        if (Array.isArray(array[length])) {
            recursion(array[length]);
        }
        console.log(array[length]);

        return array[length] + recursion(array, length + 1);
    }

    console.log(recursion(arr));

The error can be seen in the below screenshot which is the console of google chrome.

Well, the first problem you have is that JavaScript doesn't support default function arguments. (At least not in the manner you have in your code.) See MDN — Stephen Thomas
– Stephen Thomas, Commented Mar 12, 2017 at 21:27
If recursion is not required, you could accomplish this much more simply using concat and reduce: [].concat(...arr).reduce((a, b) => a + b) — Rob M.
– Rob M., Commented Mar 12, 2017 at 21:27
@StephenThomas Note, javascript does support default parameters. — guest271314
– guest271314, Commented Mar 12, 2017 at 21:29

Ted Hopp · Accepted Answer · 2017-03-12 21:43:45Z

2

You're missing a return:

...
if (Array.isArray(array[length])) {
    return recursion(array[length]);
}
...

P.S. I'd recommend changing the parameter name from length to something else (perhaps position) to avoid confusion with the length property of arrays.

edited Mar 12, 2017 at 21:43

answered Mar 12, 2017 at 21:28

Ted Hopp

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Comments

m_callens · Accepted Answer · 2017-03-12 21:33:04Z

1

You don't even need a function for this. The capability is built into Array prototypes.

const arr = [1, 2, 3, [4, 3], [10, 50], 98, 100]
const sum = [].concat(...arr).reduce((acc, curr) => acc + curr)

console.log(sum)

answered Mar 12, 2017 at 21:33

m_callens

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1 Comment

Mohammad Ajmal Amirzad Over a year ago

That is a fantastic solution friend. could you please tell me what is the concept of three dots (...arr) there?

ibrahim mahrir · Accepted Answer · 2017-03-12 21:31:17Z

1

function sum(e) {                      // take an element and return it if it's not an array or return the recursive sum if it's an array
  if(e instanceof Array) {             // if it's an array
    return e.reduce(function(s, e) {   // call sum on each item of the array and return the accumulated sum
      return s + sum(e);
    }, 0);
  }
  else                                 // else (if it's not an array) then return the item
    return e;
}

var arr = [1, 2, 3, [4, 3], [10, 50], 98, 100];

console.log(sum(arr));

answered Mar 12, 2017 at 21:31

ibrahim mahrir

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Comments

Nenad Vracar · Accepted Answer · 2017-03-12 21:31:56Z

1

Another way to do this is to use reduce()

var arr = [1, 2, 3, [4, 3],[10, 50], 98, 100];

function recursion(array) {
  return array.reduce(function(r, e) {
    return r += Array.isArray(e) ? recursion(e) : e
  }, 0)
}

console.log(recursion(arr));
console.log(recursion([1, [[[1, [[[2]]]]]]]));

answered Mar 12, 2017 at 21:31

Nenad Vracar

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Comments

guest271314 · Accepted Answer · 2017-03-12 21:34:14Z

0

Recursion is not necessary. You can use .toString(), .split(), .reduce()

var arr = [1, 2, 3, [4, 3], [10, 50], 98, 100];
var n = arr.toString().split(/,/).reduce(function(a, b) {return +a + +b});

console.log(n);

answered Mar 12, 2017 at 21:34

guest271314

1

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