Implemented VAT validation support for english (en-GB) locale

README.md

@@ -155,6 +155,7 @@ 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_valid_protocol: true, allow_underscores: false, host_whitelist: false, host_blacklist: false, allow_trailing_dot: false, allow_protocol_relative_urls: false, disallow_auth: false }`.<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/>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).
 **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/index.js

@@ -116,6 +116,8 @@ import normalizeEmail from './lib/normalizeEmail';
 
 import isSlug from './lib/isSlug';
 
+import isVAT from './lib/isVAT';
+
 const version = '13.1.17';
 
 const validator = {
@@ -215,6 +217,7 @@ const validator = {
   isSlug,
   isTaxID,
   isDate,
+  isVAT,
 };
 
 export default validator;

src/lib/isVAT.js

@@ -0,0 +1,15 @@
+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}))$/,
+};
+
+export default function isVAT(str, countryCode) {
+  assertString(str);
+  assertString(countryCode);
+
+  if (countryCode in vatMatchers) {
+    return vatMatchers[countryCode].test(str);
+  }
+  throw new Error(`Invalid country code: '${countryCode}'`);
+}

test/validators.js

@@ -9098,4 +9098,44 @@ describe('Validators', () => {
       ],
     });
   });
+
+  it('should validate english VAT numbers', () => {
+    test({
+      validator: 'isVAT',
+      args: ['GB'],
+      valid: [
+        'GB999 9999 00',
+        'GB999 9999 96',
+        'GB999999999 999',
+        'GBGD000',
+        'GBGD499',
+        'GBHA500',
+        'GBHA999',
+      ],
+      invalid: [
+        'GB999999900',
+        'GB999999996',
+        'GB999 9999 97',
+        'GB999999999999',
+        'GB999999999 9999',
+        'GB9999999999 999',
+        'GBGD 000',
+        'GBGD 499',
+        'GBHA 500',
+        'GBHA 999',
+        'GBGD500',
+        'GBGD999',
+        'GBHA000',
+        'GBHA499',
+      ],
+    });
+
+    test({
+      validator: 'isVAT',
+      args: ['invalidCountryCode'],
+      error: [
+        'GB999 9999 00',
+      ],
+    });
+  });
 });