Add is.urlInstance (#60)

readme.md

@@ -176,6 +176,17 @@ is.directInstanceOf(new UnicornError(), Error);
 //=> false
 ```
 
+##### .urlInstance(value)
+
+Returns `true` if `value` is an instance of the [`URL` class](https://developer.mozilla.org/en-US/docs/Web/API/URL).
+
+```js
+const url = new URL('https://example.com');
+
+is.urlInstance(url);
+//=> true
+```
+
 ##### .truthy(value)
 
 Returns `true` for all values that evaluate to true in a boolean context:

source/index.ts

@@ -48,7 +48,8 @@ export const enum TypeName {
 	ArrayBuffer = 'ArrayBuffer',
 	SharedArrayBuffer = 'SharedArrayBuffer',
 	DataView = 'DataView',
-	Promise = 'Promise'
+	Promise = 'Promise',
+	URL = 'URL'
 }
 
 const toString = Object.prototype.toString;
@@ -177,6 +178,7 @@ namespace is { // tslint:disable-line:no-namespace
 	export const dataView = isObjectOfType<DataView>(TypeName.DataView);
 
 	export const directInstanceOf = <T>(instance: any, klass: Class<T>): instance is T => Object.getPrototypeOf(instance) === klass.prototype;
+	export const urlInstance = (value: any): value is URL => isObjectOfType<URL>(TypeName.URL)(value);
 
 	export const truthy = (value: any) => Boolean(value);
 	export const falsy = (value: any) => !value;

source/tests/test.ts

@@ -3,6 +3,7 @@ import net from 'net';
 import Stream from 'stream';
 import util from 'util';
 import tempy from 'tempy';
+import {URL} from 'url';
 import test, {TestContext, Context} from 'ava';
 import {JSDOM} from 'jsdom';
 import {Subject, Observable} from 'rxjs';
@@ -534,6 +535,14 @@ test('is.directInstanceOf', t => {
 	t.false(m.directInstanceOf(errorSubclass, Error));
 });
 
+test('is.urlInstance', t => {
+	const url = new URL('https://www.example.com');
+	t.true(m.urlInstance(url));
+	t.false(m.urlInstance({}));
+	t.false(m.urlInstance(undefined));
+	t.false(m.urlInstance(null));
+});
+
 test('is.truthy', t => {
 	t.true(m.truthy('unicorn'));
 	t.true(m.truthy('🦄'));