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

To query an array of strings for a regular expression match in MongoDB, use the regular expression pattern directly in the find query. MongoDB automatically searches through array elements and matches any string that satisfies the regex pattern.

Syntax

db.collection.find({ arrayField: /regexPattern/ })

Create Sample Data

db.queryArrayDemo.insertMany([
    {
        "StudentFullName": [
            "Carol Taylor",
            "Caroline Williams", 
            "Claire Brown"
        ]
    },
    {
        "StudentFullName": [
            "John Smith",
            "Jace Doe",
            "Jabin Brown"
        ]
    }
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5ca2774c6304881c5ce84ba0"),
        ObjectId("5ca277b36304881c5ce84ba1")
    ]
}

Display All Documents

db.queryArrayDemo.find().pretty()

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

Example: Query Array with Regex Match

Find documents where any array element starts with "J" ?

db.queryArrayDemo.find({ StudentFullName: /^J/ })

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

More Examples

Case-Insensitive Search

db.queryArrayDemo.find({ StudentFullName: /carol/i })

Contains Pattern

db.queryArrayDemo.find({ StudentFullName: /Brown/ })

Conclusion

MongoDB automatically searches through array elements when using regex patterns. Use /^pattern/ for starts-with matching and /pattern/i for case-insensitive searches across string arrays.