$substrCP

The $substrCP operator returns a substring from a string, measured in UTF-8 code points (characters), starting at a specified character index with a specified number of characters.

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📌 Syntax

{ "$substrCP": [ <string>, <startChar>, <charLength> ] }

• <string>: The input string
• <startChar>: Character index to start from (0-based)
• <charLength>: Number of characters (code points) to return

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✅ Base Example 1 – Extract First 4 Characters

📥 Input Document

{ "title": "Notebook" }

📌 Expression

{ "$substrCP": ["$title", 0, 4] }

📤 Output

"Note"

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✅ Base Example 2 – Multilingual Safe Slicing

📥 Input Document

{ "label": "नमस्ते" }

📌 Expression

{ "$substrCP": ["$label", 0, 3] }

📤 Output

"नमस्"

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🧱 Ecommerce Example – Shorten Product Names

📌 Pipeline

[
  { "$unwind": "$items" },
  {
    "$project": {
      "shortName": {
        "$substrCP": ["$items.name", 0, 6]
      }
    }
  }
]

📥 Input Document

{
  "items": [
    { "name": "Bluetooth Speaker" },
    { "name": "Wireless Keyboard" }
  ]
}

📤 Output

[
  { "shortName": "Blueto" },
  { "shortName": "Wirele" }
]

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🔧 Common Use Cases

• Multilingual-safe substring extraction
• Character-length-limited output
• Text formatting for display

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🔗 Related Operators

• $substr, $substrBytes, $split, $slice, $strLenCP

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🧠 Notes

• Use $substrCP over $substr or $substrBytes for Unicode strings.
• Avoid cutting emojis or multibyte characters with $substrBytes.

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