Merge sorted arrays into one (JavaScript)

merge_sorted_arrays.js

var sorted_lists = [
    [3, 4, 6, 10, 11, 15],
    [1, 5, 8, 12, 14, 19],
    [2, 7, 9, 13, 16, 17, 18],
    [20, 22, 23, 25]
];

function mergeSortedArrays(sortedLists) {
    var pointers = new Array(sortedLists.length);

    for (var i = 0; i < pointers.length; i++) {
        pointers[i] = 0;
    }

    var mergedPointer = 0;
    var totalLength = 0;

    sortedLists.forEach(function(item) {
        totalLength += item.length;
    });

    var merged = new Array(totalLength);

    while(mergedPointer < totalLength) {
        var args = [];

        for (var i =0; i < sortedLists.length; i++) {
            args.push(sortedLists[i][pointers[i]]);
        }

        var minIndex = getMinIndex(args);

        merged[mergedPointer] = sortedLists[minIndex][pointers[minIndex]];
        pointers[minIndex]++;
        mergedPointer++;
    }

    return merged;

    function getMinIndex(list) {
        var min = list[0];
        var minIndex = 0;

        for(var i = 1; i < list.length; i++) {
            if (list[i] && (!min || list[i] < min)) {
                min = list[i];
                minIndex = i;
            }
        }

        return minIndex;
    }
}

console.log(mergeSortedArrays(sorted_lists));