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$regexMatch

The $regexMatch operator evaluates whether a string input matches a regular expression pattern.

📌 Syntax

{
  "$regexMatch": {
    "input": <string>,
    "regex": <pattern>,
    "options": <string>
  }
}
  • input: The string to test.
  • regex: The pattern to match.
  • options: Optional flags like "i" (case-insensitive), "m" (multiline), etc.

✅ Base Example 1 – Match Case-Insensitive Word

📥 Input Document

{ "name": "Wireless Mouse" }

📌 Expression

{
  "$regexMatch": {
    "input": "$name",
    "regex": "mouse",
    "options": "i"
  }
}

📤 Output

true

✅ Base Example 2 – Validate Product ID Format

📥 Input Document

{ "productId": "ABC-1234" }

📌 Expression

{
  "$regexMatch": {
    "input": "$productId",
    "regex": "^[A-Z]{3}-\d{4}$"
  }
}

📤 Output

true

🧱 Ecommerce Example – Check Brand Label Format

📌 Pipeline

[
  { "$unwind": "$items" },
  {
    "$project": {
      "brandValid": {
        "$regexMatch": {
          "input": "$items.brand",
          "regex": "^[A-Z]{4,6}$"
        }
      },
      "product": "$items.name"
    }
  }
]

📥 Input Document

{
  "items": [
    { "name": "TV", "brand": "SONY" },
    { "name": "Book", "brand": "bk01" }
  ]
}

📤 Output

[
  { "brandValid": true, "product": "TV" },
  { "brandValid": false, "product": "Book" }
]

🔧 Common Use Cases

  • Format validation (e.g., SKU, ID)
  • Keyword searching
  • Input sanitization
  • $regexFind, $regexFindAll, $regexMatch, $toLower, $split

🧠 Notes

  • Use \ to escape characters like \d in JSON.
  • Combine with $cond or $match for rule evaluation.