range_recursive_sum

// The sum of a range
function range(start, end) {
    var x = Array();
    if (start <= end) {
        do { x.push(start); start++; } while (start <= end);
        return x;
    }
    else {
        do { x.push(start); start-- } while (end <= start);
        return x;
    }
}
// Recursive
function sum(n) {
    if (n[-1] != n[0]) {
        var z = n.pop();
        return sum(n) + z;
    }
    else{
        return 0;
    }
}
console.log(sum(range(-1,-10)));