How to wait for a mongoose .exec() function to finish before returning?

Question

I have the following function involving mongoose:

  let username = userObject.username;
  Purchase.find({
    account: username,
    fufilled: true 
  })
    .populate("keys")
    .exec(function(err, foundPurchases) {
      if (err) {
        return inStockItems;
      } else {
        if (foundPurchases.length === 0) {
          return inStockItems;
        } else {
          // these lists will be a list of IDs of game detail entries in the database
          let listOfReceivedIds = foundPurchases.keys.map(obj => obj.game);

          for (let i = 0; i < inStockItems.length; i++) {
            if (inStockItems.length <= minimum) {
              return inStockItems;
            }

            let currentProductAnalysing = inStockItems[i];
            if (listOfReceivedIds.includes(currentProductAnalysing._id)) {
              console.log("removing product");
              inStockItems.splice(i, 1);
            }
          }
          return inStockItems;
        }
      }
    });

I am running the function like the following, which returns undefined

inStockItems = function_name(inStockItems, userObject, amount);

How can I rewrite the function so that the function returns the value of inStockItems and not undefined. Thanks.

Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — FZs, Nov 09 '19 at 22:53

score 0 · Accepted Answer · answered Nov 09 '19 at 21:05

.exec in Mongoose returns a promise of the query result if you don't give it a callback. Your function here needs to be calling .exec() and changing its return value to return something different from the function like this:

async function function_name(inStockItems, userObject, amount) {
  const foundPurchases = await Purchase.find({
      account: username,
      fufilled: true
    })
    .populate("keys")
    .exec();
  if (foundPurchases.length === 0) {
    return inStockItems;
  } else {
    let listOfReceivedIds = foundPurchases.keys.map(obj => obj.game);

    for (let i = 0; i < inStockItems.length; i++) {
      if (inStockItems.length <= minimum) {
        return inStockItems;
      }

      let currentProductAnalysing = inStockItems[i];
      if (listOfReceivedIds.includes(currentProductAnalysing._id)) {
        console.log("removing product");
        inStockItems.splice(i, 1);
      }
    }
    return inStockItems;
  }
}

The other alternative would be to pass a callback parameter to your function and call it from the exec() callback but promises are generally cleaner to work with.

I'll check this out tomorrow, but thank you very much for your time. — , Nov 09 '19 at 22:05

How to wait for a mongoose .exec() function to finish before returning?

1 Answers1