Regex Patterns

const EMAIL = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

EMAIL.test("user@example.com");      // true
EMAIL.test("user.name+tag@co.uk");  // true
EMAIL.test("no-at-sign");           // false

// Matches http/https URLs
const URL_PATTERN = /^https?:\/\/(www\.)?[-a-zA-Z0-9@:%._+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_+.~#?&/=]*)$/;

URL_PATTERN.test("https://example.com");          // true
URL_PATTERN.test("http://sub.domain.co/path?q=1"); // true
URL_PATTERN.test("not a url");                    // false

// International format (+1 555 123 4567, +91-9876543210, etc.)
const PHONE_INTL = /^\+?[\d\s\-().]{7,15}$/;

// US format only (555-123-4567 / (555) 123-4567)
const PHONE_US = /^(\+1\s?)?(\(?\d{3}\)?[\s.\-]?\d{3}[\s.\-]?\d{4})$/;

PHONE_INTL.test("+1 (555) 123-4567"); // true
PHONE_US.test("(555) 123-4567");      // true
PHONE_US.test("555.123.4567");        // true

// At least 8 chars: uppercase, lowercase, digit, special character
const STRONG_PASSWORD = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[\W_]).{8,}$/;

// At least 6 chars: letter and number
const MEDIUM_PASSWORD = /^(?=.*[a-zA-Z])(?=.*\d).{6,}$/;

STRONG_PASSWORD.test("Passw0rd!"); // true
MEDIUM_PASSWORD.test("pass12");    // true

// Generic 13–19 digit card number (with optional spaces/dashes)
const CREDIT_CARD = /^[\d\s\-]{13,19}$/;

// Specific card types
const VISA       = /^4[\d]{12}(?:[\d]{3})?$/;
const MASTERCARD = /^5[1-5][\d]{14}$/;
const AMEX       = /^3[47][\d]{13}$/;

VISA.test("4532015112830366");  // true
AMEX.test("378282246310005");  // true

// IPv4
const IPV4 = /^(25[0-5]|2[0-4]\d|[01]?\d\d?)(\.(25[0-5]|2[0-4]\d|[01]?\d\d?)){3}$/;

// IPv6 (simplified)
const IPV6 = /^([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}$/;

IPV4.test("192.168.1.1");  // true
IPV4.test("999.1.1.1");   // false

// 3 or 6 digit hex color
const HEX_COLOR = /^#([0-9A-Fa-f]{3}|[0-9A-Fa-f]{6})$/;

// With or without #
const HEX_COLOR_OPT = /^#?([0-9A-Fa-f]{3}|[0-9A-Fa-f]{6})$/;

HEX_COLOR.test("#fff");     // true
HEX_COLOR.test("#1a2b3c"); // true
HEX_COLOR.test("fff");     // false

// YYYY-MM-DD
const DATE_ISO = /^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$/;

// DD/MM/YYYY or DD-MM-YYYY
const DATE_DMY = /^(0[1-9]|[12]\d|3[01])[/\-](0[1-9]|1[0-2])[/\-]\d{4}$/;

// MM/DD/YYYY
const DATE_MDY = /^(0[1-9]|1[0-2])\/(0[1-9]|[12]\d|3[01])\/\d{4}$/;

DATE_ISO.test("2024-11-08"); // true
DATE_DMY.test("08/11/2024"); // true
DATE_MDY.test("11/08/2024"); // true

const UUID = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;

UUID.test("550e8400-e29b-41d4-a716-446655440000"); // true
UUID.test("not-a-uuid");                           // false

// URL-safe slug: lowercase letters, numbers, hyphens
const SLUG = /^[a-z0-9]+(?:-[a-z0-9]+)*$/;

SLUG.test("hello-world");   // true
SLUG.test("my-post-2024");  // true
SLUG.test("Hello World");   // false
SLUG.test("--double--");    // false

// 3–20 chars, letters/numbers/underscores/hyphens, must start with a letter
const USERNAME = /^[a-zA-Z][a-zA-Z0-9_-]{2,19}$/;

USERNAME.test("john_doe");   // true
USERNAME.test("alice123");   // true
USERNAME.test("1startNum"); // false
USERNAME.test("ab");         // false (too short)

const ZIP_US    = /^\d{5}(-\d{4})?$/;             // US: 12345 or 12345-6789
const POSTAL_CA = /^[A-Za-z]\d[A-Za-z][ -]?\d[A-Za-z]\d$/; // Canada: A1B 2C3
const POSTAL_UK = /^[A-Z]{1,2}\d[A-Z\d]? ?\d[A-Z]{2}$/i;   // UK: SW1A 2AA

ZIP_US.test("12345");       // true
ZIP_US.test("12345-6789");  // true
POSTAL_CA.test("A1B 2C3"); // true

// Match any HTML tag
const HTML_TAG = /<[^>]*>/g;

// Strip all tags
"<h1>Hello</h1> <p>World</p>".replace(HTML_TAG, ""); // "Hello World"

const INTEGER       = /^-?\d+$/;
const FLOAT         = /^-?\d+(\.\d+)?$/;
const POSITIVE_INT  = /^\d+$/;
const COMMA_NUMBER  = /^-?\d{1,3}(,\d{3})*(\.\d+)?$/;

INTEGER.test("-42");          // true
FLOAT.test("3.14");           // true
COMMA_NUMBER.test("1,234.56"); // true