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title Regex Operators
description Pattern matching with regular expressions using $regex and $match

Regex Operators

New in v5.2.0 - Match strings using powerful regular expression patterns.

Overview

Regex operators provide flexible pattern matching beyond simple string operations. Use them for:

  • Email validation
  • Phone number formatting
  • URL pattern matching
  • Date format validation
  • Custom pattern validation

$regex - Regular Expression Match

Match strings using JavaScript regular expressions.

Basic Usage

import { filter } from '@mcabreradev/filter';

const users = [
  { email: 'user@gmail.com' },
  { email: 'admin@company.com' },
  { email: 'test@GMAIL.com' }
];

// Case-insensitive email matching
filter(users, {
  email: { $regex: /@gmail\.com$/i }
});
// → [{ email: 'user@gmail.com' }, { email: 'test@GMAIL.com' }]

Pattern Validation

const products = [
  { sku: 'PROD-001-A' },
  { sku: 'PROD-002-B' },
  { sku: 'SERV-001-A' }
];

// Match SKU pattern: PROD-###-X
filter(products, {
  sku: { $regex: /^PROD-\d{3}-[A-Z]$/ }
});
// → [{ sku: 'PROD-001-A' }, { sku: 'PROD-002-B' }]

Phone Number Validation

const contacts = [
  { phone: '+1-555-0100' },
  { phone: '555-0200' },
  { phone: '+1-555-0300' }
];

// Match format: +1-###-####
filter(contacts, {
  phone: { $regex: /^\+1-\d{3}-\d{4}$/ }
});
// → [{ phone: '+1-555-0100' }, { phone: '+1-555-0300' }]

$match - Alias for $regex

$match is a more intuitive alias for $regex:

// These are equivalent:
filter(users, { email: { $regex: /^admin/ } });
filter(users, { email: { $match: /^admin/ } });

Complex Patterns

URL Validation

const links = [
  { url: 'https://example.com/api/v1/users' },
  { url: 'http://test.com/admin' },
  { url: 'https://example.com/api/v2/products' }
];

// Match HTTPS API endpoints (v1 or v2)
filter(links, {
  url: { $regex: /^https:\/\/.*\/api\/v[12]\// }
});
// → HTTPS API v1 and v2 endpoints only

Date Format Matching

const records = [
  { date: '2025-01-15' },
  { date: '01/15/2025' },
  { date: '2025-02-20' }
];

// Match YYYY-MM-DD format
filter(records, {
  date: { $regex: /^\d{4}-\d{2}-\d{2}$/ }
});
// → [{ date: '2025-01-15' }, { date: '2025-02-20' }]

Username Validation

const users = [
  { username: 'john_doe' },
  { username: 'jane.smith' },
  { username: 'user123' },
  { username: 'invalid user' }
];

// Alphanumeric with underscore, 3-20 characters
filter(users, {
  username: { $regex: /^[a-zA-Z0-9_]{3,20}$/ }
});
// → [{ username: 'john_doe' }, { username: 'user123' }]

Performance Considerations

::: warning Performance Note Regex operators are powerful but slower than simple string operators. Use $startsWith, $endsWith, or $contains when possible.

Performance Ranking (fastest to slowest):

  1. Simple string matching
  2. Object-based filtering
  3. String operators ($startsWith, $endsWith, $contains)
  4. Regex operators ← You are here
  5. Predicate functions :::

Optimization Tips

// ⚠️ Slower: Regex for simple matching
filter(users, { email: { $regex: /@gmail\.com$/ } });

// ✅ Faster: String operator
filter(users, { email: { $endsWith: '@gmail.com' } });

// ⚠️ Slower: Regex for prefix
filter(products, { name: { $regex: /^Laptop/ } });

// ✅ Faster: String operator
filter(products, { name: { $startsWith: 'Laptop' } });

Real-World Examples

Email Domain Filtering

const users = [
  { email: 'user@gmail.com' },
  { email: 'admin@company.com' },
  { email: 'test@outlook.com' }
];

// Match common email providers
filter(users, {
  email: { $regex: /@(gmail|outlook|yahoo)\.com$/i }
});

Credit Card Validation

const payments = [
  { card: '4111-1111-1111-1111' },
  { card: '5500-0000-0000-0004' },
  { card: 'invalid' }
];

// Match Visa cards (start with 4, 16 digits)
filter(payments, {
  card: { $regex: /^4\d{3}-\d{4}-\d{4}-\d{4}$/ }
});

IP Address Validation

const logs = [
  { ip: '192.168.1.1' },
  { ip: '10.0.0.1' },
  { ip: 'invalid' }
];

// Simple IP pattern (not perfect but practical)
filter(logs, {
  ip: { $regex: /^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/ }
});

Combining with Other Operators

// Regex + comparison operators
filter(products, {
  sku: { $regex: /^PROD-/ },
  price: { $gte: 100, $lte: 500 }
});

// Regex + logical operators
filter(users, {
  $or: [
    { email: { $regex: /@gmail\.com$/i } },
    { email: { $regex: /@outlook\.com$/i } }
  ],
  isActive: true
});

Case Sensitivity

// Case-insensitive (use 'i' flag)
filter(users, {
  email: { $regex: /@GMAIL\.COM$/i }  // Matches any case
});

// Case-sensitive (no flag)
filter(users, {
  email: { $regex: /@gmail\.com$/ }  // Exact case only
});

Common Patterns

Alphanumeric

{ field: { $regex: /^[a-zA-Z0-9]+$/ } }

Email

{ email: { $regex: /^[^\s@]+@[^\s@]+\.[^\s@]+$/ } }

Phone (US)

{ phone: { $regex: /^\+?1?\d{10}$/ } }

URL

{ url: { $regex: /^https?:\/\/.+/ } }

Hex Color

{ color: { $regex: /^#[0-9A-Fa-f]{6}$/ } }

Next Steps

::: tip Best Practice Use regex operators for complex patterns that can't be expressed with simple string operators. For basic prefix/suffix/substring matching, prefer $startsWith, $endsWith, and $contains. :::