MongoDB $abs operator

MongoDB provides different types of arithmetic expression operators that are used in the aggregation pipeline stages and $abs operator is one of them. This operator is used to find the absolute value of the specified number.  

Syntax: 

{ $abs: <number> }

Here, the number is a valid expression until it resolves to a number. 

• If the entered value is null, then this operator will return null.
• If the entered value is NaN, then this operator will return NaN.
• If the entered value is a missing field, then this operator will return null.

Examples:

In the following examples, we are working with:

Database: GeeksforGeeks

Collection: Employee

Document: three documents that contain the details of the employees in the form of field-value pairs.

Using $abs operator:

In this example, we are going to find the total salary of every employee in the development department. 

db.Employee.aggregate([{$match: {department: "Development"}},
... {$project: {name:1, tSalary: {$abs: 
                {$add: ["$firstSalary", "$secondSalary"]}}}}])

Using $abs operator in embedded documents:

In this example, we are going to find a total of three months’ salary of the employee in the HR department. 

db.Employee.aggregate([{$match: {department: "HR"}},
... {$project: {name: 1, tSalary: {$abs: 
                {$add: ["$salary.firstMonth",
                        "$salary.secondMonth", 
                        "$salary.thirdMonth"]}}}}])