Removing an array element from MongoDB collection using update() and $pull

Let us first create a collection with documents -

> db.removingAnArrayElementDemo.insertOne({"UserMessage":["Hi","Hello","Bye"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cef97bdef71edecf6a1f6a4")
}

Display all documents from a collection with the help of find() method -

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

Output

{
   "_id" : ObjectId("5cef97bdef71edecf6a1f6a4"),
   "UserMessage" : [
      "Hi",
      "Hello",
      "Bye"
   ]
}

Following is the query to remove an array element from MongoDB -

> db.removingAnArrayElementDemo.update(
   {_id:ObjectId("5cef97bdef71edecf6a1f6a4")},
   { "$pull": { "UserMessage": "Hello" } }
);
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Let us check the document once again:

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

Output

{
   .
   "_id" : ObjectId("5cef97bdef71edecf6a1f6a4"),
   "UserMessage" : [
      "Hi",
      "Bye"
   ]
}