$type

The $type operator returns a string that identifies the BSON type of the input value.

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📌 Syntax

{ "$type": <expression> }

Returns values such as "string", "int", "double", "date", "bool", "object", "array", etc.

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✅ Base Example – Detect Type

📥 Input Document

{ "price": 99.99 }

📌 Expression

{ "$type": "$price" }

📤 Output

"double"

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✅ Type of Nested Field

📥 Input Document

{ "metadata": { "tags": ["new", "hot"] } }

📌 Expression

{ "$type": "$metadata.tags" }

📤 Output

"array"

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🧱 Ecommerce Example – Validate Price Type Before Conversion

📌 Pipeline

[
  {
    "$project": {
      "product": "$name",
      "priceType": { "$type": "$price" },
      "price": 1
    }
  }
]

📥 Input Documents

[
  { "name": "Phone", "price": "699" },
  { "name": "Laptop", "price": 1499.99 }
]

📤 Output

[
  { "product": "Phone", "priceType": "string", "price": "699" },
  { "product": "Laptop", "priceType": "double", "price": 1499.99 }
]

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🔧 Common Use Cases

• Debug complex fields before transformation
• Conditional conversion or validation
• Auditing unknown schemas

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🔗 Related Operators

• $convert, $ifNull, $cond, $literal

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🧠 Notes

• Useful when working with inconsistent or dynamic data sources
• Helps avoid runtime conversion errors

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