How to Insert Array in MongoDB: Syntax and Examples

To insert an array in MongoDB, include the array as a value in the document object passed to insertOne() or insertMany(). MongoDB stores arrays natively, so you just assign the array to a field like { items: [1, 2, 3] }.

Syntax

Use the insertOne() method on a collection to add a document. The document can have fields with array values. Arrays are enclosed in square brackets [] and can contain any data type.

• db.collection.insertOne(document): Inserts one document.
• document: An object with fields and values, where values can be arrays.

javascript

db.collection.insertOne({ fieldName: [value1, value2, value3] })

Example

This example inserts a document with an array field tags containing three strings. It shows how MongoDB stores arrays directly inside documents.

javascript

db.products.insertOne({ name: "Notebook", tags: ["stationery", "paper", "office"] })

Output

{ acknowledged: true, insertedId: ObjectId("someObjectId") }

Common Pitfalls

Common mistakes include:

• Using parentheses () instead of square brackets [] for arrays.
• Trying to insert arrays as strings instead of actual arrays.
• Not using valid JSON-like syntax for documents.

Always ensure arrays are properly formatted and passed as arrays, not strings.

javascript

/* Wrong: array as string */
db.collection.insertOne({ items: "[1, 2, 3]" })

/* Right: array as array */
db.collection.insertOne({ items: [1, 2, 3] })

Quick Reference

Remember these tips when inserting arrays in MongoDB:

• Use square brackets [] for arrays.
• Arrays can contain mixed data types.
• Insert arrays as part of the document object.
• Use insertOne() or insertMany() to add documents.

Key Takeaways

Insert arrays by including them as field values in the document object.

Use square brackets [] to define arrays in MongoDB documents.

Avoid passing arrays as strings; always use actual array syntax.

Use insertOne() or insertMany() methods to insert documents with arrays.

MongoDB stores arrays natively and supports mixed data types inside arrays.