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Array Update Operators

$each

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  • Definition
  • Behavior
  • Examples

Definition

$each

The $each modifier is available for use with the $addToSet operator and the $push operator.

Use with the $addToSet operator to add multiple values to an array <field> if the values do not exist in the <field>.

{ $addToSet: { <field>: { $each: [ <value1>, <value2> ... ] } } }

Use with the $push operator to append multiple values to an array <field>.

{ $push: { <field>: { $each: [ <value1>, <value2> ... ] } } }

The $push operator can use $each modifier with other modifiers. For a list of modifiers available for $push, see Modifiers.

Behavior

Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order. See Update Operators Behavior for details.

Examples

Use $each with $push Operator

The following example appends each element of [ 90, 92, 85 ] to the scores array for the document where the name field equals joe:

db.students.updateOne(
   { name: "joe" },
   { $push: { scores: { $each: [ 90, 92, 85 ] } } }
)

Use $each with $addToSet Operator

A collection inventory has the following document:

{ _id: 2, item: "cable", tags: [ "electronics", "supplies" ] }

Then the following operation uses the $addToSet operator with the $each modifier to add multiple elements to the tags array:

db.inventory.updateOne(
   { _id: 2 },
   { $addToSet: { tags: { $each: [ "camera", "electronics", "accessories" ] } } }
 )

The operation only adds "camera" and "accessories" to the tags array. "electronics" was already in the array:

{
  _id: 2,
  item: "cable",
  tags: [ "electronics", "supplies", "camera", "accessories" ]
}

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