How to change the type of a field in MongoDB?

MongoDB allows you to change the data type of existing fields using update operations with type conversion functions. Let us convert a string type field to number type using the parseInt() function with an update query.

Sample Data

First, create a collection with a document containing different data types ?

db.changeDataType.insertOne({
    "StudentName": "Larry",
    "StudentAge": 23,
    "StudentZipCode": "10001",
    "isProgrammer": false
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5c6ed4976fd07954a4890694")
}

Display the document to verify the data ?

db.changeDataType.find().pretty();

{
    "_id": ObjectId("5c6ed4976fd07954a4890694"),
    "StudentName": "Larry",
    "StudentAge": 23,
    "StudentZipCode": "10001",
    "isProgrammer": false
}

Check Current Field Types

Use the typeof operator to check the current data types of each field ?

checkType = db.changeDataType.findOne();
typeof checkType._id;
typeof checkType.StudentName;
typeof checkType.StudentAge;
typeof checkType.StudentZipCode;
typeof checkType.isProgrammer;

object
string
number
string
boolean

Convert String to Number Type

Now change the StudentZipCode field from string to number type using forEach() and parseInt() ?

db.changeDataType.find().forEach(function(doc) {
    db.changeDataType.update(
        {"_id": doc._id},
        {"$set": {
            "StudentZipCode": parseInt(doc.StudentZipCode)
        }}
    );
});

Verify the Type Change

Check the updated document and verify the data type conversion ?

updatedDoc = db.changeDataType.findOne();

{
    "_id": ObjectId("5c6ed4976fd07954a4890694"),
    "StudentName": "Larry",
    "StudentAge": 23,
    "StudentZipCode": 10001,
    "isProgrammer": false
}

Confirm the type change ?

typeof updatedDoc.StudentZipCode;

number

Conclusion

MongoDB doesn't support direct field type conversion, but you can change field types by updating documents with type conversion functions like parseInt(), parseFloat(), or toString() using the $set operator.