Given a JavaScript array, function flattens the array and returns the sum of all primitive-type numbers in the array. The function works recursively.

flattenAndAdd.js

/*
Given a JavaScript array, function flattens the array and returns the sum of all primitive-type numbers in the array.
The function works recursively.
*/

function flattenAndAdd(arrayToFlatten) {

    var originalArray = arrayToFlatten;
    var repeat = 1;

    var flatArray = (function checkObject() {
        while (repeat > 0) {
            repeat = 0;
            for (var n in originalArray) {
                if (typeof originalArray[n] === "object") {
                    for (var nN in originalArray[n]) {
                        originalArray.push(originalArray[n][nN]);
                        repeat += 1;
                    }
                }
            }
        }
        return originalArray;
    })();

    var finalSum = (function () {
        var sum = 0,
            m;
        for (m in flatArray) {
            if (typeof flatArray[m] === "number") {
                sum += flatArray[m];
            }
        }
        return sum;
    })();
    
    console.log(finalSum);
    return finalSum;
}