$anyElementTrue (aggregation)

On this page

Definition

Behavior
Example

This version of the documentation is archived and no longer supported. View the current documentation to learn how to upgrade your version of MongoDB.

Definition

$anyElementTrue

Evaluates an array as a set and returns true if any of the elements are true and false otherwise. An empty array returns false.

$anyElementTrue has the following syntax:

{ $anyElementTrue: [ <expression> ] }

The <expression> itself must resolve to an array, separate from the outer array that denotes the argument list. For more information on expressions, see Expressions.

Behavior

If a set contains a nested array element, $anyElementTrue does not descend into the nested array but evaluates the array at top-level.

In addition to the false boolean value, $anyElementTrue evaluates as false the following: null, 0, and undefined values. The $anyElementTrue evaluates all other values as true, including non-zero numeric values and arrays.

Example	Result
`{ $anyElementTrue: [ [ true, false ] ] }`	`true`
`{ $anyElementTrue: [ [ [ false ] ] ] }`	`true`
`{ $anyElementTrue: [ [ null, false, 0 ] ] }`	`false`
`{ $anyElementTrue: [ [ ] ] }`	`false`

Example

Create an example collection named survey with the following documents:

db.survey.insertMany([
   { "_id" : 1, "responses" : [ true ] },
   { "_id" : 2, "responses" : [ true, false ] },
   { "_id" : 3, "responses" : [ ] },
   { "_id" : 4, "responses" : [ 1, true, "seven" ] },
   { "_id" : 5, "responses" : [ 0 ] },
   { "_id" : 6, "responses" : [ [ ] ] },
   { "_id" : 7, "responses" : [ [ 0 ] ] },
   { "_id" : 8, "responses" : [ [ false ] ] },
   { "_id" : 9, "responses" : [ null ] },
   { "_id" : 10, "responses" : [ undefined ] }
])

The following operation uses the $anyElementTrue operator to determine if the responses array contains any value that evaluates to true:

db.survey.aggregate(
   [
     { $project: { responses: 1, isAnyTrue: { $anyElementTrue: [ "$responses" ] }, _id: 0 } }
   ]
)

The operation returns the following results:

{ "responses" : [ true ], "isAnyTrue" : true }
{ "responses" : [ true, false ], "isAnyTrue" : true }
{ "responses" : [ ], "isAnyTrue" : false }
{ "responses" : [ 1, true, "seven" ], "isAnyTrue" : true }
{ "responses" : [ 0 ], "isAnyTrue" : false }
{ "responses" : [ [ ] ], "isAnyTrue" : true }
{ "responses" : [ [ 0 ] ], "isAnyTrue" : true }
{ "responses" : [ [ false ] ], "isAnyTrue" : true }
{ "responses" : [ null ], "isAnyTrue" : false }
{ "responses" : [ undefined ], "isAnyTrue" : false }

Back

$and (aggregation)

$arrayElemAt (aggregation)