NodeJs Mongoose Value Showing as undefined

Question

So basically what I'm trying to do is the following, I have a webpage where I create a grocery list (on the press of the button, I send a post request with a list of items) and then do some actions on the so-called grocery list

Each Item objects consists of a ItemCode, Item Price and Name:

This is Part of my grocerylist Controller

    exports.creategroceryList = asyncHandler(async (req, res, next) => {
  req.body.user = req.user.id;
  const gl = await GroceryList.create(req.body);
  fixedloop(req.body); // Create an updated grocerylist
  res.status(201).json({
    success: true,
    data: gl,
  });
});

In the Same controller Class I also have

    function fixedloop(obj) {
  obj.listofItems.forEach((item) => {
    for (let key in item) {
      if (key == "ItemCode") {
        Items.findOne({ ItemCode: item[key] }).then((data) => {
          f(data);
        });
        function f(data) {
          ftempdoc = data;
          console.log(" Came from f Funct " + ftempdoc);
        }
        Items2.findOne({ ItemCode: item[key] }).then((data) => {
          f1(data);
        });
        function f1(data) {
          stempdoc = data;
          console.log(" Came from f1 Funct " + stempdoc);
        }
        Items.findOne({ ItemCode: item[key] }).then((data) => {
          f2(data);
        });
        function f2(data) {
          fprice = data.ItemPrice;
          console.log(" Came from f2 Funct " + fprice);
        }
        Items2.findOne({ ItemCode: item[key] }).then((data) => {
          f3(data);
        });
        function f3(data) {
          sprice = data.ItemPrice;
          console.log(" Came from f3 Funct " + sprice);
        }
        if (fprice < sprice) {
          flist.push(ftempdoc);
        } else {
          slist.push(stempdoc);
        }
      }
    }
  });
  console.log(flist);
  console.log(slist);
  data2 = {
    firstlistofItems: flist,
    secondlistofItems: slist,
  };
  console.log("end");
  const gl = UGroceryList.create(data2);
}

Simply Explained, I have the global variables and what I'm trying to do is go over the list of items that I got from the create grocerylist, and check from two different mongo schemas the price of each item, I then insert into a list the cheapest prices like shown,

the problems are that first I see the end part and a list of undefined.

Answer 1

In python index starts at 0, here you have to use range(0,5) to take this into account:

my_list=[0]*5
for i in range(0,5):
    my_list[i]=(i-1)*10
print(my_list)

as to fill your vector properly.

Answer 2

List indexing starts at zero and the 2nd parameter of range is a stop value (i.e. 5 is not included), so you can break down the process in your mind (or on paper):

                               # my_list          i      (i-1)*10
my_list=[0]*5                  # [0, 0, 0, 0, 0]
for i in range(1,5):           #                  1..4
    my_list[i]=(i-1)*10        # [0,00, 0, 0, 0]  1      00
                               # [0, 0,10, 0, 0]  2      10
                               # [0, 0,10,20, 0]  3      20
                               # [0, 0,10,20,30]  4      30  
print(my_list)

If you are looking to obtain [0,10,20,30,40] you have to think in terms of zero-based indexing:

my_list = [0]*5
for i in range(5):      # 0..4   range(5) is the same as range(0,5)
    my_list[i] = i*10