$add

The `$add` operator adds numbers together or adds numbers and dates. When adding numbers and dates, the numbers are interpreted as milliseconds.

Syntax

{ $add: [ <listOfExpressions> ] }

Parameters

<listOfExpressions>stringrequired

Any valid expressions that resolve to numbers or dates. The expressions can be any combination of numbers and dates.

Examples

Sample Data

{
  "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
  "staff": { "totalStaff": { "fullTime": 8, "partTime": 20 } }
}

Get the current and project staff count

Calculate the total staff and project the total staff looking forward using the $add operator.

Query:

db.stores.aggregate([
  { $match: { _id: "40d6f4d7-50cd-4929-9a07-0a7a133c2e74" } },
  {
    $project: {
      name: 1,
      currentTotalStaff: { $add: ["$staff.totalStaff.fullTime", "$staff.totalStaff.partTime"] },
      projectedNextYearStaff: { $add: ["$staff.totalStaff.fullTime", "$staff.totalStaff.partTime", 2] }
    }
  }
])

Output:

[
  {
    "_id": "40d6f4d7-50cd-4929-9a07-0a7a133c2e74",
    "name": "Proseware, Inc. | Home Entertainment Hub",
    "currentTotalStaff": 39,
    "projectedNextYearStaff": 41
  }
]