MongoDB Array Update Operator - $pop

MongoDB $pop

In MongoDB, the $pop operator removes the first or last element of an array. The value -1 is used with $pop to remove the first element of an array and 1 for the last element.

Syntax:

db.collection.update( {field: value }, { $pop: { field: [1 | -1] } } );

Parameters:

Sample collection "student"

{
        "_id" : 1,
        "sem" : 1,
        "achieve" : [
                70,
                87,
                90,
                90,
                65,
                81
        ]
}

Example of MongoDB $pop to remove the last element

If we want to remove the last element from the array field achieve for any instance of 70 in this array, the following mongodb command can be used -

> db.student.update( {achieve: 70 }, { $pop: { achieve : 1 } } );

To see the newly updated document -

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

Output of the command:

{ "_id" : 1, "achieve" : [ 70, 87, 90, 90, 65 ], "sem" : 1 }

Example of MongoDB $pop to remove first element

If we want to remove the first element from the array field achieve for any instance of 70 in this array, the following mongodb command can be used -

> db.student.update( {achieve: 70 }, { $pop: { achieve : -1 } } );

To see the newly updated document -

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

Output of the command

{ "_id" : 1, "achieve" : [ 87, 90, 90, 65, 81 ], "sem" : 1 }

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