Update object at specific Array Index in MongoDB?

To update object at specific array index in MongoDB, use the $set operator with dot notation to target the exact position in nested arrays. Specify the array path with numeric indices to access objects at specific locations.

Syntax

db.collection.update(
    { "field": "value" },
    { $set: { "arrayName.index1.index2.fieldName": "newValue" } }
);

Sample Data

Let us first create a collection with nested array structure:

db.updateObjectDemo.insertOne({
    id: 101,
    "StudentDetails": [
        [
            { "StudentName": "John" },
            { "StudentName": "Chris" }
        ],
        [
            { "StudentName": "Carol" },
            { "StudentName": "David" }
        ]
    ]
});

{
    "acknowledged": true,
    "insertedId": ObjectId("5ccdcd9b685b30d09a7111e0")
}

Display the current document structure:

db.updateObjectDemo.find().pretty();

{
    "_id": ObjectId("5ccdcd9b685b30d09a7111e0"),
    "id": 101,
    "StudentDetails": [
        [
            { "StudentName": "John" },
            { "StudentName": "Chris" }
        ],
        [
            { "StudentName": "Carol" },
            { "StudentName": "David" }
        ]
    ]
}

Example: Update Object at Index [1,1]

Update the StudentName at position [1,1] from "David" to "Mike":

db.updateObjectDemo.update(
    { "id": 101 },
    { $set: { "StudentDetails.1.1.StudentName": "Mike" } }
);

WriteResult({ "nMatched": 1, "nUpserted": 0, "nModified": 1 })

Verify Result

Check if the object at index [1,1] has been updated:

db.updateObjectDemo.find().pretty();

{
    "_id": ObjectId("5ccdcd9b685b30d09a7111e0"),
    "id": 101,
    "StudentDetails": [
        [
            { "StudentName": "John" },
            { "StudentName": "Chris" }
        ],
        [
            { "StudentName": "Carol" },
            { "StudentName": "Mike" }
        ]
    ]
}

Key Points

• Use dot notation with numeric indices to access nested array elements
• StudentDetails.1.1 targets the second array's second element
• Array indexing starts from 0 in MongoDB

Conclusion

Use $set with dot notation and numeric indices to update objects at specific positions in nested arrays. The syntax arrayName.index1.index2.fieldName provides precise control over which element to modify.