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node.jsmongodbmongoosedatabase

What is returned from Mongoose query that finds no matches?

I'm a little confused reading the Mongoose documentation.

If I run a query in mongoose which matches no documents in the collection, what are the values of err and results in the callback function callback(err, results)? I just don't know what Mongoose considers an "error". As a mathematician, returning the empty set (i.e. results array empty) seems perfectly valid and shouldn't be an "error" - the query executed fine, there was just no matching documents. On the other hand, some may consider it an "error". From mongoose docs, either:

  1. err = null, results = []
  2. err = null, results = null
  3. err = error document, results = null
Solution

  • It depends on the query. If it is a find, then results == []. If it is a findOne, then results == null. No errors if everything else is ok.