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EJSON.serialize()

The EJSON.serialize() method converts BSON objects to Extended JSON representation as JavaScript objects.

MongoDB stores data using BSON. Many external data transformation applications use JSON. You can use EJSON.serialize() to convert BSON to JSON and save the output for those external applications.

Syntax

The method has this syntax:

EJSON.serialize( object, [ options ] )

Method Fields

The method takes the following fields:

Field

Type

Necessity

Description

object

BSON object

Required

BSON object to convert. For example, an array of documents.

options

string

Optional

Modifies the output object types. The only option is { relaxed: <boolean> }.

Boolean Value	Description
`true`	Return JSON object types. Default is `true`.
`false`	Return BSON object types.

Behavior

You can run EJSON.serialize() from an interactive mongosh session or from the system command line using --eval.

To run EJSON.serialize() from an interactive mongosh session, use:

EJSON.serialize( object, [ options ] )

To run EJSON.serialize() from the system command line, use:

mongosh --eval "EJSON.serialize( object, [ options ] )"

Examples

Create the sales collection for the examples:

db.sales.insertMany( [
   { custId: 345, purchaseDate: ISODate("2023-07-04"),
     quantity: 4, cost: Decimal128("100.60") },
   { custId: 346, purchaseDate: ISODate("2023-07-12"),
     quantity: 3, cost: Decimal128("175.45") },
   { custId: 486, purchaseDate: ISODate("2023-08-01"),
     quantity: 9, cost: Decimal128("200.53") }
] )

Interactive Mongo Shell EJSON.serialize() Example

The following example retrieves the sales documents as an array and stores the results in the salesCollection object:

salesCollection = EJSON.serialize( db.sales.find().toArray() )

Example output, which uses JSON:

[
   {
      _id: { '$oid': '6520519a0dbd2d208a5c7941' },
      custId: 345,
      purchaseDate: { '$date': '2023-07-04T00:00:00Z' },
      quantity: 4,
      cost: { '$numberDecimal': '100.60' }
   },
   {
      _id: { '$oid': '6520519a0dbd2d208a5c7942' },
      custId: 346,
      purchaseDate: { '$date': '2023-07-12T00:00:00Z' },
      quantity: 3,
      cost: { '$numberDecimal': '175.45' }
   },
   {
      _id: { '$oid': '6520519a0dbd2d208a5c7943' },
      custId: 486,
      purchaseDate: { '$date': '2023-08-01T00:00:00Z' },
      quantity: 9,
      cost: { '$numberDecimal': '200.53' }
   }
]

Command Line Mongo Shell EJSON.serialize() Example

To save collection data to a file, you can use EJSON.serialize() with the mongosh --eval method.

The following example retrieves the sales documents as an array and saves the results to a file named sales.json on the computer's file system:

# Note: The example is formatted to fit the page.
mongosh --quiet \
        --eval "EJSON.serialize( db.sales.find().toArray() )" \
        > sales.json

You could then use the sales.json file with an external data transformation application.

Learn More

EJSON serialize method
EJSON documentation

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parse()

stringify()