Javascript unlimited nested array handling

Question

I am trying to have fun with my buddy who solved the problem mentioned in 8m 7s, and for me it is already 20m gone. I can't figure out how to handle unlimited nested array in javascript.

The problem is this:

// i will be an array, containing integers, strings and/or arrays like itself.
// Sum all the integers you find, anywhere in the nest of arrays.

So

arraySum([[1,2,false],'4','5']) will return 3 (passed)
arraySum([[1,2,3],4,5]) will return 15 (passed)
arraySum([[[[[[[[[1]]]]]]]], 1]) will return 2 (failed)

The code I wrote is:

function arraySum(i) {

sum = 0;
tmp =0;
for (var a=0; a<i.length; a++){
    if (i[a] instanceof Array) {
        ar = i[a];
        for (var j=0; j<ar.length; j++){
            tmp +=ar[j];
        }
    }
    if (typeof i[a] == "number")
        sum += i[a];
        console.log(sum);
}
return sum + tmp;

}

As you can see it does not handle the last situation that I failed as I can't figure out how to handle unlimited nest in JS.

Any idea will be much appreciated. Also try to finish it before 8m 7s, which my buddy finished in.

Answer 1

Inside of the if (i[a] instanceof Array) { part, you'll have to use recursion to operate on nested arrays with the same arraySum function, not just use another loop. Try this:

var arraySum = (function () {
    "use strict";

    var sumFunc, isArray;

    sumFunc = function (arr) {
        var sum, i, j, cur, toAdd;

        sum = 0;

        for (i = 0, j = arr.length; i < j; i++) {
            cur = arr[i];

            toAdd = 0;
            if (isArray(cur)) {
                toAdd = sumFunc(cur);
            } else if (typeof cur === "number") {
                toAdd = cur;
            }

            sum += toAdd;
        }

        return sum;
    };

    isArray = Array.isArray || function (obj) {
        return Object.prototype.toString.call(obj) === "[object Array]";
    };

    return sumFunc;
}());

DEMO: http://jsfiddle.net/Q7JPM/1

The function just loops through all items in an array, and returns the sum of any numbers found inside. If the item is an array itself, it calls arraySum and passes that array...adding the result to the sum. If it's a number, it simply adds that to the sum.