How to check if field is a number in MongoDB?

To check if field is a number in MongoDB, use the $type operator. Following is the syntax

db.yourCollectionName.find({youtFieldName: {$type:"number"}}).pretty();

Let us first create a collection with documents

> db.checkIfFieldIsNumberDemo.insertOne({"StudentName":"John","StudentAge":23});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c9ec75dd628fa4220163b83")
}
>db.checkIfFieldIsNumberDemo.insertOne({"StudentName":"Chris","StudentMathScore":98,"StudentCountryName":"US"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c9ec77cd628fa4220163b84")
}
>db.checkIfFieldIsNumberDemo.insertOne({"StudentName":"Robert","StudentCountryName":"AUS"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c9ec7a4d628fa4220163b85")
}
>db.checkIfFieldIsNumberDemo.insertOne({"StudentId":101,"StudentName":"Larry","StudentCountryName":"AUS"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c9ec7ccd628fa4220163b86")
}

Following is the query to display all documents from a collection with the help of find() method

> db.checkIfFieldIsNumberDemo.find().pretty();

This will produce the following output

{
   "_id" : ObjectId("5c9ec75dd628fa4220163b83"),
   "StudentName" : "John",
   "StudentAge" : 23
}
{
   "_id" : ObjectId("5c9ec77cd628fa4220163b84"),
   "StudentName" : "Chris",
   "StudentMathScore" : 98,
   "StudentCountryName" : "US"
}
{
   "_id" : ObjectId("5c9ec7a4d628fa4220163b85"),
   "StudentName" : "Robert",
   "StudentCountryName" : "AUS"
}
{
   "_id" : ObjectId("5c9ec7ccd628fa4220163b86"),
   "StudentId" : 101,
   "StudentName" : "Larry",
   "StudentCountryName" : "AUS"
}

Following is the query to check if a field is a number

> db.checkIfFieldIsNumberDemo.find({StudentMathScore: {$type:"number"}}).pretty();

The following is the output displaying the field which is a number i.e. StudentMathScore

{
   "_id" : ObjectId("5c9ec77cd628fa4220163b84"),
   "StudentName" : "Chris",
   "StudentMathScore" : 98,
   "StudentCountryName" : "US"
}