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$toUpper

The $toUpper operator converts a string to all uppercase letters.

📌 Syntax

{ "$toUpper": <expression> }

The expression must resolve to a string.

✅ Base Example 1 – Uppercase City Name

📥 Input Document

{ "city": "toronto" }

📌 Expression

{ "$toUpper": "$city" }

📤 Output

"TORONTO"

✅ Base Example 2 – Uppercase Username for Display

📥 Input Document

{ "username": "janedoe" }

📌 Expression

{ "$toUpper": "$username" }

📤 Output

"JANEDOE"

🧱 Ecommerce Example – Uppercase Category Labels

📌 Pipeline

[
  { "$unwind": "$items" },
  {
    "$project": {
      "categoryUpper": { "$toUpper": "$items.category" },
      "product": "$items.name"
    }
  }
]

📥 Input Document

{
  "items": [
    { "name": "Shoes", "category": "fashion" },
    { "name": "Tablet", "category": "electronics" }
  ]
}

📤 Output

[
  { "categoryUpper": "FASHION", "product": "Shoes" },
  { "categoryUpper": "ELECTRONICS", "product": "Tablet" }
]

🔧 Common Use Cases

  • Case normalization
  • Visual formatting for UI
  • Standardizing categories and labels
  • $toLower, $trim, $concat, $substr, $toString

🧠 Notes

  • Input must be a string.
  • Combine with $ifNull or $cond to avoid null errors.