How to query an Array[String] for a Regular Expression match?

To query an array string for a regexp match, use the following syntax

db.yourCollectionName.find( { yourFieldName: /yourStartingValue./ } ).pretty();

Let us first create a collection with documents

> db.queryArrayDemo.insertOne({"StudentFullName":["Carol Taylor","Caroline
Williams","Claire Brown"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ca2774c6304881c5ce84ba0")
}
> db.queryArrayDemo.insertOne({"StudentFullName":["John Smith","Jace Doe","Jabin
Brown"]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ca277b36304881c5ce84ba1")
}

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

> db.queryArrayDemo.find().pretty();

This will produce the following output

{
   "_id" : ObjectId("5ca2774c6304881c5ce84ba0"),
   "StudentFullName" : [
      "Carol Taylor",
      "Caroline Williams",
      "Claire Brown"
   ]
}
{
   "_id" : ObjectId("5ca277b36304881c5ce84ba1"),
   "StudentFullName" : [
      "John Smith",
      "Jace Doe",
      "Jabin Brown"
   ]
}

Here is how you can query an array string for a regexp match

> db.queryArrayDemo.find( { StudentFullName : /J./ } ).pretty();

This will produce the following output

{
   "_id" : ObjectId("5ca277b36304881c5ce84ba1"),
   "StudentFullName" : [
      "John Smith",
      "Jace Doe",
      "Jabin Brown"
   ]
}