MongoDB regular expression to match a specific record?

Let us first create a collection with documents −

> dbworkingOfRegularExpressionDemoinsertOne({ "StudentDetails" : { "StudentName" : "John" },"StudentAge":21 });
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cf227acb64a577be5a2bc07")
}
> dbworkingOfRegularExpressionDemoinsertOne({ "StudentDetails" : { "StudentName" : "JOHN" },"StudentAge":19 });
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cf227b8b64a577be5a2bc08")
}
> dbworkingOfRegularExpressionDemoinsertOne({ "StudentDetails" : { "StudentName" : "Carol" },"StudentAge":20 });
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cf227c2b64a577be5a2bc09")
}

Following is the query to display all documents from a collection with the help of find() method −

> dbworkingOfRegularExpressionDemofind();

This will produce the following document −

{ "_id" : ObjectId("5cf227acb64a577be5a2bc07"), "StudentDetails" : { "StudentName" : "John" }, "StudentAge" : 21 }
{ "_id" : ObjectId("5cf227b8b64a577be5a2bc08"), "StudentDetails" : { "StudentName" : "JOHN" }, "StudentAge" : 19 }
{ "_id" : ObjectId("5cf227c2b64a577be5a2bc09"), "StudentDetails" : { "StudentName" : "Carol" }, "StudentAge" : 20 }
Following is the regular expression to get the document with StudentName JOHN:
> dbworkingOfRegularExpressionDemofind({'StudentDetailsStudentName': /JOHN/});

This will produce the following document −

{ "_id" : ObjectId("5cf227b8b64a577be5a2bc08"), "StudentDetails" : { "StudentName" : "JOHN" }, "StudentAge" : 19 }