$eq (expression operator)

Definition

$eq

Compares two values and returns:

• true when the values are equivalent.

• false when the values are not equivalent.

The $eq compares both value and type, using the specified BSON comparison order for values of different types.

$eq has this syntax:

{ $eq: [ <expression1>, <expression2> ] }

The arguments can be any valid expression. For more information on expressions, see Expressions.

Example

The following example uses the movies collection from the sample_mflix sample dataset. For details on how to load this dataset into your deployment, see Load the sample dataset.

This aggregation operation uses the $eq operator to determine if the year field equals 1978:

db.movies.aggregate( [   { $match: { runtime: { $gt: 1000 } } },   {      $project:        {          _id: 0,          title: 1,          year: 1,          yearEq1978: { $eq: [ "$year", 1978 ] }        }   }] )

[  {    title: 'Centennial',    year: 1978,    yearEq1978: true  },  {    title: 'Baseball',    year: 1994,    yearEq1978: false  }]