MongoDB: How to query documents by rounding a specific field

Question

Let's suppose there is the following collection of documents in MongoDB:

Scores

{ _id: 1, value: 3.25 }
{ _id: 2, value: 1.37 }
{ _id: 3, value: 2.48 }
{ _id: 4, value: 2.5 }

I would like to query documents with the rounded value of 3 . So it will return { _id: 1, value: 3.25 } and { _id: 4, value: 2.5 } only.

The Node.js query would be something like db.collection('scores').find({...})

What do I need to put in the query?

Answer 1

I am not sure it possible to directly using any query operators,

you can prepare condition on the client-side by number's minimum and maximum value boundry, just prepare a function like,

function getValueCondition(n) {
  return { 
    $gte: Math.round(n) - 0.5, 
    $lt: Math.round(n) + 0.5
  };
}

You query would be and get condition,

let inputNumber = 3;
db.collection('scores').find({ 
  value: getValueCondition(inputNumber)
});