How does a Mongoose callback function know what the second parameter is the db.query result?

Question

How does the anonymous callback function know that 'item' (or really the second argument in the following callback function after Mongoose queries since they can be called anything) in the below example is/are supposed to be the result(s) from the database, if any? Since we can call 'item' anything really, I don't see the line of communication here.

Thanks!

Item.find( { name: req.body.item.name }, function(err, item) {

Answer 1

It's a positional parameter. It calls your function with two parameters, and that's the second one.