Added isOctal validator including tests and updated README.

README.md

@@ -126,6 +126,7 @@ Validator                               | Description
 **isMongoId(str)**                      | check if the string is a valid hex-encoded representation of a [MongoDB ObjectId][mongoid].
 **isMultibyte(str)**                    | check if the string contains one or more multibyte chars.
 **isNumeric(str [, options])**                      | check if the string contains only numbers.<br/><br/>`options` is an object which defaults to `{no_symbols: false}`. If `no_symbols` is true, the validator will reject numeric strings that feature a symbol (e.g. `+`, `-`, or `.`).
+**isOctal(str)**                        | check if the string is a valid octal number.
 **isPort(str)**                         | check if the string is a valid port number.
 **isPostalCode(str, locale)**           | check if the string is a postal code,<br/><br/>(locale is one of `[ 'AD', 'AT', 'AU', 'BE', 'BG', 'BR', 'CA', 'CH', 'CZ', 'DE', 'DK', 'DZ', 'EE', 'ES', 'FI', 'FR', 'GB', 'GR', 'HR', 'HU', 'ID', 'IE' 'IL', 'IN', 'IS', 'IT', 'JP', 'KE', 'LI', 'LT', 'LU', 'LV', 'MT', 'MX', 'NL', 'NO', 'NZ', 'PL', 'PR', 'PT', 'RO', 'RU', 'SA', 'SE', 'SI', 'TN', 'TW', 'UA', 'US', 'ZA', 'ZM' ]` OR 'any'. If 'any' is used, function will check if any of the locals match. Locale list is `validator.isPostalCodeLocales`.).
 **isSurrogatePair(str)**                | check if the string contains any surrogate pairs chars.

src/index.js

@@ -33,6 +33,7 @@ import isInt from './lib/isInt';
 import isFloat, { locales as isFloatLocales } from './lib/isFloat';
 import isDecimal from './lib/isDecimal';
 import isHexadecimal from './lib/isHexadecimal';
+import isOctal from './lib/isOctal';
 import isDivisibleBy from './lib/isDivisibleBy';
 
 import isHexColor from './lib/isHexColor';
@@ -135,6 +136,7 @@ const validator = {
   isFloatLocales,
   isDecimal,
   isHexadecimal,
+  isOctal,
   isDivisibleBy,
   isHexColor,
   isISRC,

src/lib/isOctal.js

@@ -0,0 +1,8 @@
+import assertString from './util/assertString';
+
+const octal = /^(0o)?[0-7]+$/i;
+
+export default function isOctal(str) {
+  assertString(str);
+  return octal.test(str);
+}

test/validators.js

@@ -2504,6 +2504,24 @@ describe('Validators', () => {
     });
   });
 
+  it('should validate octal strings', () => {
+    test({
+      validator: 'isOctal',
+      valid: [
+        '076543210',
+        '0o01234567',
+      ],
+      invalid: [
+        'abcdefg',
+        '012345678',
+        '012345670c',
+        '00c12345670c',
+        '',
+        '..',
+      ],
+    });
+  });
+
   it('should validate hexadecimal color strings', () => {
     test({
       validator: 'isHexColor',