How do you remove an array element by its index in MongoDB

To remove array element by its index in MongoDB, you can use $unset and $pull operator. There are two steps to remove array elements from an array.The syntax for the same is as follows:

db.yourCollectionName.update({},{$unset:{"yourArrayListName.yourPosition":yourPositionValue}};
db.yourCollectionName.update({},{$pull:{"yourArrayListName":null}});

To understand the above syntax, let us create a collection with document. The query to create a collection with document is as follows:

>db.removeArrayElements.insertOne({"StudentName":"Larry","StudentAge":23,"TechnicalSub
ject":["C","C++","Java","MongoDB"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c6ea4879c4643706aef56d2")
}

Display all documents from a collection with the help of find() method. The query is as follows:

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

The following is the output:

{
   "_id" : ObjectId("5c6ea4879c4643706aef56d2"),
   "StudentName" : "Larry",
   "StudentAge" : 23,
   "TechnicalSubject" : [
      "C",
      "C++",
      "Java",
      "MongoDB"
   ]
}

Here is the query to remove array element by its index:

> db.removeArrayElements.update({},{$unset:{"TechnicalSubject.3":1}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

> db.removeArrayElements.update({},{$pull:{"TechnicalSubject":null}});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Above, we have removed array element “MongoDB”, which is at index 3. Let us display documents from a collection. The query is as follows:

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

The following is the output:

{
   "_id" : ObjectId("5c6ea4879c4643706aef56d2"),
   "StudentName" : "Larry",
   "StudentAge" : 23,
   "TechnicalSubject" : [
      "C",
      "C++",
      "Java"
   ]
}

Look at the above sample output, the index 3 i.e. position 4 has been removed from the array i.e. the element “MongoDB”.