Add isTwitterHandle validator

- Add new validator for Twitter handles (@username format)
- Accepts handles with or without @ symbol
- 1-15 characters, letters, numbers, and underscores only
- Add comprehensive test cases covering valid/invalid scenarios
- Update README.md documentation
- Export validator in main index

Fixes validation for Twitter usernames/handles for Hacktoberfest contribution.

Author: dollaransh17

README.md

@@ -167,6 +167,7 @@ Validator                               | Description
 **isStrongPassword(str [, options])**   | check if the string can be considered a strong password or not. Allows for custom requirements or scoring rules. If `returnScore` is true, then the function returns an integer score for the password rather than a boolean.<br/>Default options: <br/>`{ minLength: 8, minLowercase: 1, minUppercase: 1, minNumbers: 1, minSymbols: 1, returnScore: false, pointsPerUnique: 1, pointsPerRepeat: 0.5, pointsForContainingLower: 10, pointsForContainingUpper: 10, pointsForContainingNumber: 10, pointsForContainingSymbol: 10 }`
 **isTime(str [, options])**             | check if the string is a valid time e.g. [`23:01:59`, new Date().toLocaleTimeString()].<br/><br/> `options` is an object which can contain the keys `hourFormat` or `mode`.<br/><br/>`hourFormat` is a key and defaults to `'hour24'`.<br/><br/>`mode` is a key and defaults to `'default'`. <br/><br/>`hourFormat` can contain the values `'hour12'` or `'hour24'`, `'hour24'` will validate hours in 24 format and `'hour12'` will validate hours in 12 format. <br/><br/>`mode` can contain the values `'default', 'withSeconds', withOptionalSeconds`, `'default'` will validate `HH:MM` format, `'withSeconds'` will validate the `HH:MM:SS` format, `'withOptionalSeconds'` will validate `'HH:MM'` and `'HH:MM:SS'` formats.
 **isTaxID(str, locale)**                | check if the string is a valid Tax Identification Number. Default locale is `en-US`.<br/><br/>More info about exact TIN support can be found in `src/lib/isTaxID.js`.<br/><br/>Supported locales: `[ 'bg-BG', 'cs-CZ', 'de-AT', 'de-DE', 'dk-DK', 'el-CY', 'el-GR', 'en-CA', 'en-GB', 'en-IE', 'en-US', 'es-AR', 'es-ES', 'et-EE', 'fi-FI', 'fr-BE', 'fr-CA', 'fr-FR', 'fr-LU', 'hr-HR', 'hu-HU', 'it-IT', 'lb-LU', 'lt-LT', 'lv-LV', 'mt-MT', 'nl-BE', 'nl-NL', 'pl-PL', 'pt-BR', 'pt-PT', 'ro-RO', 'sk-SK', 'sl-SI', 'sv-SE', 'uk-UA']`.
+**isTwitterHandle(str)**                | check if the string is a valid Twitter handle (username). Accepts handles with or without the `@` symbol. Handle must be 1-15 characters long and can contain letters, numbers, and underscores only.
 **isURL(str [, options])**              | check if the string is a URL.<br/><br/>`options` is an object which defaults to `{ protocols: ['http','https','ftp'], require_tld: true, require_protocol: false, require_host: true, require_port: false, require_valid_protocol: true, allow_underscores: false, host_whitelist: false, host_blacklist: false, allow_trailing_dot: false, allow_protocol_relative_urls: false, allow_fragments: true, allow_query_components: true, disallow_auth: false, validate_length: true }`.<br/><br/>`protocols` - valid protocols can be modified with this option.<br/>`require_tld` - If set to false isURL will not check if the URL's host includes a top-level domain.<br/>`require_protocol` - if set to true isURL will return false if protocol is not present in the URL.<br/>`require_host` - if set to false isURL will not check if host is present in the URL.<br/>`require_port` - if set to true isURL will check if port is present in the URL.<br/>`require_valid_protocol` - isURL will check if the URL's protocol is present in the protocols option.<br/>`allow_underscores` - if set to true, the validator will allow underscores in the URL.<br/>`host_whitelist` - if set to an array of strings or regexp, and the domain matches none of the strings defined in it, the validation fails.<br/>`host_blacklist` - if set to an array of strings or regexp, and the domain matches any of the strings defined in it, the validation fails.<br/>`allow_trailing_dot` - if set to true, the validator will allow the domain to end with a `.` character.<br/>`allow_protocol_relative_urls` - if set to true protocol relative URLs will be allowed.<br/>`allow_fragments` - if set to false isURL will return false if fragments are present.<br/>`allow_query_components` - if set to false isURL will return false if query components are present.<br/>`disallow_auth` - if set to true, the validator will fail if the URL contains an authentication component, e.g. `http://username:password@example.com`.<br/>`validate_length` - if set to false isURL will skip string length validation. `max_allowed_length` will be ignored if this is set as `false`.<br/>`max_allowed_length` - if set, isURL will not allow URLs longer than the specified value (default is 2084 that IE maximum URL length).<br/>
 **isULID(str)**                         | check if the string is a [ULID](https://github.com/ulid/spec).
 **isUUID(str [, version])**             | check if the string is an RFC9562 UUID.<br/>`version` is one of `'1'`-`'8'`, `'nil'`, `'max'`, `'all'` or `'loose'`. The `'loose'` option checks if the string is a UUID-like string with hexadecimal values, ignoring RFC9565.

src/index.js

@@ -127,6 +127,7 @@ import normalizeEmail from './lib/normalizeEmail';
 import isSlug from './lib/isSlug';
 import isLicensePlate from './lib/isLicensePlate';
 import isStrongPassword from './lib/isStrongPassword';
+import isTwitterHandle from './lib/isTwitterHandle';
 
 import isVAT from './lib/isVAT';
 
@@ -240,6 +241,7 @@ const validator = {
   isSlug,
   isStrongPassword,
   isTaxID,
+  isTwitterHandle,
   isDate,
   isTime,
   isLicensePlate,
@@ -248,3 +250,4 @@ const validator = {
 };
 
 export default validator;
+export { default as isTwitterHandle } from './lib/isTwitterHandle';

src/lib/isTwitterHandle.js

@@ -0,0 +1,10 @@
+import assertString from './util/assertString';
+
+/* eslint-disable no-control-regex */
+const twitterHandle = /^@?[A-Za-z0-9_]{1,15}$/;
+/* eslint-enable no-control-regex */
+
+export default function isTwitterHandle(str) {
+  assertString(str);
+  return twitterHandle.test(str);
+}

test/validators.test.js

@@ -15911,4 +15911,49 @@ describe('Validators', () => {
       ],
     });
   });
+  it('should validate Twitter handles', () => {
+    test({
+      validator: 'isTwitterHandle',
+      valid: [
+        '@twitter',
+        '@github',
+        '@validatorjs',
+        '@user123',
+        '@test_user',
+        '@a',
+        '@123456789012345', // 15 characters
+        'twitter', // without @ symbol
+        'github',
+        'validatorjs',
+        'user123',
+        'test_user',
+        'a',
+        '123456789012345',
+        'a_b_c_d_e_f_g_h',
+        'USER123', // case insensitive
+        'Test_User',
+      ],
+      invalid: [
+        '@1234567890123456', // 16 characters (too long)
+        '@user-name', // hyphen not allowed
+        '@user name', // space not allowed
+        '@user.name', // dot not allowed
+        '@user@name', // @ not allowed in middle
+        '@user+name', // plus not allowed
+        '@user#name', // hash not allowed
+        '@user$name', // dollar not allowed
+        '@', // empty handle
+        '', // empty string
+        '@@twitter', // double @
+        '@user!', // exclamation not allowed
+        '@user?', // question mark not allowed
+        '@user*', // asterisk not allowed
+        '@user%', // percent not allowed
+        'user-name', // hyphen not allowed even without @
+        'user name', // space not allowed even without @
+        'user.name', // dot not allowed even without @
+        '1234567890123456', // 16 characters (too long) without @
+      ],
+    });
+  });
 });