Store a JavaScript Function on the Server
Note
Do not store application logic in the database. There are performance limitations to running JavaScript inside of MongoDB. Application code also is typically most effective when it shares version control with the application itself.
There is a special system collection named system.js
that can store
JavaScript functions for reuse.
To store a function, you can use the db.collection.insertOne()
, as
in the following examples:
db.system.js.insertOne( { _id: "echoFunction", value : function(x) { return x; } } ); db.system.js.insertOne( { _id : "myAddFunction" , value : function (x, y){ return x + y; } } );
The
_id
field holds the name of the function and is unique per database.The
value
field holds the function definition.
These functions, saved as BSON type JavaScript, are available for use from any JavaScript
context, such as mapReduce
and $where
.
Functions saved as the deprecated BSON type JavaScript (with
scope), however, cannot be used by
mapReduce
and $where
starting in MongoDB 4.4.