added dutch VAT check

for hacktober validatorjs#1742

if you want to extend it more check :
https://www.oreilly.com/library/view/regular-expressions-cookbook/9781449327453/ch04s21.html

README.md

@@ -159,7 +159,7 @@ Validator                               | Description
 **isURL(str [, options])**              | check if the string is an 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/>require_protocol - if set as true isURL will return false if protocol is not present in the URL.<br/>require_valid_protocol - isURL will check if the URL's protocol is present in the protocols option.<br/>protocols - valid protocols can be modified with this option.<br/>require_host - if set as false isURL will not check if host is present in the URL.<br/>require_port - if set as true isURL will check if port is present in the URL.<br/>allow_protocol_relative_urls - if set as true protocol relative URLs will be allowed.<br/>allow_fragments - if set as false isURL will return false if fragments are present.<br/>allow_query_components - if set as false isURL will return false if query components are present.<br/>validate_length - if set as false isURL will skip string length validation (2083 characters is IE max URL length).
 **isUUID(str [, version])**             | check if the string is a UUID (version 3, 4 or 5).
 **isVariableWidth(str)**                | check if the string contains a mixture of full and half-width chars.
-**isVAT(str, countryCode)**                | checks that the string is a [valid VAT number](https://en.wikipedia.org/wiki/VAT_identification_number) if validation is available for the given country code matching [ISO 3166-1 alpha-2](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2). <br/><br/>Available country codes: `[ 'GB', 'IT' ]`.
+**isVAT(str, countryCode)**                | checks that the string is a [valid VAT number](https://en.wikipedia.org/wiki/VAT_identification_number) if validation is available for the given country code matching [ISO 3166-1 alpha-2](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2). <br/><br/>Available country codes: `[ 'GB', 'IT','NL' ]`.
 **isWhitelisted(str, chars)**           | checks characters if they appear in the whitelist.
 **matches(str, pattern [, modifiers])** | check if string matches the pattern.<br/><br/>Either `matches('foo', /foo/i)` or `matches('foo', 'foo', 'i')`.
 

src/lib/isVAT.js

@@ -3,6 +3,7 @@ import assertString from './util/assertString';
 export const vatMatchers = {
   GB: /^GB((\d{3} \d{4} ([0-8][0-9]|9[0-6]))|(\d{9} \d{3})|(((GD[0-4])|(HA[5-9]))[0-9]{2}))$/,
   IT: /^(IT)?[0-9]{11}$/,
+  NL: /^(NL)?[0-9]{9}B[0-9]{2}$/,
 };
 
 export default function isVAT(str, countryCode) {

test/validators.js

@@ -11015,7 +11015,7 @@ describe('Validators', () => {
       ],
     });
   });
-  it('should validate english VAT numbers', () => {
+  it('should validate VAT numbers', () => {
     test({
       validator: 'isVAT',
       args: ['GB'],
@@ -11045,7 +11045,6 @@ describe('Validators', () => {
         'GBHA499',
       ],
     });
-
     test({
       validator: 'isVAT',
       args: ['IT'],
@@ -11061,7 +11060,21 @@ describe('Validators', () => {
         'IT123456789',
       ],
     });
-
+    test({
+      validator: 'isVAT',
+      args: ['NL'],
+      valid: [
+        'NL123456789B10',
+        '123456789B10',
+      ],
+      invalid: [
+        'NL12345678 910',
+        'NL 123456789101',
+        'NL123456789B1',
+        'GB12345678910',
+        'NL123456789',
+      ],
+    });
     test({
       validator: 'isVAT',
       args: ['invalidCountryCode'],