You asked for a sorting algorithm or a function which merged two arrays.

Merge Sort In Javascript

function merge(array_one, array_two)
{
    var new_array_length = array_one.length + array_two.length;
    var array_three = new Array(new_array_length);
    var p_one = 0;
    var p_two = 0;
    for (var p_three = 0; p_three < new_array_length; p_three++)
    {
        if (array_one.length == p_one)
        {
            array_three[p_three] = array_two[p_two];
            p_two++;    
        }
        else if (array_two.length == p_two)
        {
            array_three[p_three] = array_one[p_one];
            p_one++;
        }
        else if (array_one[p_one] <= array_two[p_two])
        {
            array_three[p_three] = array_one[p_one];
            p_one++;
        }
        else
        {
            array_three[p_three] = array_two[p_two];
            p_two++;
        }
    }
    return array_three;
}

function merge_sort(an_array)
{
    if (1 == an_array.length)
    {
        return an_array;
    }
    else
    {
        var mid = Math.floor(an_array.length / 2);
        return merge(
            merge_sort(an_array.slice(0, mid)),
            merge_sort(an_array.slice(mid, an_array.length)));
    }
}