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MongoDB – $each Modifier
  • Last Updated : 10 May, 2020
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MongoDB provides different types of array update operators to update the values of the array fields in the documents and $each modifier is one of them. This modifier is used to append multiple values to the array field. You can use this modifier with $addToSet and $push operators:

$each modifier with $addToSet operator –
If you use $each modifier with $addToSet operator, then it adds multiple values to an array field if the specified value does not present in the array field.
Syntax:

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

$each modifier with $push operator –
If you use $each modifier with $push operator, then it appends multiple values to an array field. The $push operator is allowed to use $each modifier with other modifiers ( like, $slice, $sort, and $position).
Syntax:

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

In the following examples, we are working with:

Database: GeeksforGeeks
Collection: contributor
Document: two documents that contain the details of the contributor in the form of field-value pairs.



Using $each modifier with $addToSet operator:

In this example, we are updating a contributor’s document whose name is Sumit using $each modifier with $addToSet operator. Here, this operation only adds “Ruby” and “C” in the language field and does not add “Java”, “C#” because they already exists in the language field.




db.contributor.update({name: "Sumit"}, 
... {$addToSet: {language: {$each: ["Ruby", "Java", "C", "C#"]}}})

Using $each modifier with $push operator:

In this example, we are updating a contributor’s document whose name is Rohit using $each modifier with $push operator. Here, this operation appends the specified value, i.e., [“Java”, “C”, “Python”] to the end of the language field. It does not remove duplicate values.




db.contributor.update({name: "Rohit"}, 
... {$push: {language: {$each: ["Java", "C", "Python"]}}})


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