Introduction to MongoDB $pop Operator
The MongoDB $pop
operator is used to remove the first or last element from an array.
Syntax
The syntax of the $pop
operator is as follows:
{ $pop: { <field>: <-1 | 1> } }
Where:
<field>
represents the array field to operate on.<-1 | 1>
is used to specify the position of the element to be removed. -1 means to remove the last element of the array, and 1 means to remove the first element of the array.
Use cases
The $pop
operator is commonly used in the following scenarios:
- Remove the first or last element of an array.
- When you need to remove an element from an array, using the
$pop
operator is more convenient.
Examples
Here are two examples of using the $pop
operator.
Example 1
Assume there is a users
collection that contains the following document:
{
"_id": 1,
"username": "user1",
"scores": [3, 6, 9]
}
To remove the last element from the scores
array, you can use the following command:
db.users.updateOne({ _id: 1 }, { $pop: { scores: -1 } })
After executing this command, the value of the scores
array is [3, 6]
.
Example 2
Continuing with the users
collection above, if you want to remove the first element from the scores
array, you can use the following command:
db.users.updateOne({ _id: 1 }, { $pop: { scores: 1 } })
After executing this command, the value of the scores
array is [6, 9]
.
Conclusion
Through this article, we learned that the $pop
operator is used to remove the first or last element from an array and is commonly used in scenarios where array elements need to be removed.