From 119c41d39bfdf598a3b235bf5f88f6f7adc5d5d7 Mon Sep 17 00:00:00 2001
From: Or Schneider <or.schneider.1993@gmail.com>
Date: Sun, 24 Sep 2017 22:26:15 +0300
Subject: [PATCH] Add `is.class()` (#2)

---
 index.js  |  4 +++-
 readme.md |  4 ++++
 test.js   | 12 ++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/index.js b/index.js
index 132db41..78b4368 100644
--- a/index.js
+++ b/index.js
@@ -130,11 +130,13 @@ is.plainObject = x => {
 	// eslint-disable-next-line no-return-assign
 	return getObjectType(x) === 'Object' &&
 		(prototype = Object.getPrototypeOf(x), prototype === null ||
-		prototype === Object.getPrototypeOf({}));
+			prototype === Object.getPrototypeOf({}));
 };
 
 is.iterable = x => !is.null(x) && !is.undefined(x) && typeof x[Symbol.iterator] === 'function';
 
+is.class = x => typeof x === 'function' && x.toString().startsWith('class ');
+
 const typedArrayTypes = new Set([
 	'Int8Array',
 	'Uint8Array',
diff --git a/readme.md b/readme.md
index ee1761d..45ade28 100644
--- a/readme.md
+++ b/readme.md
@@ -115,6 +115,10 @@ JavaScript primitives are as follows: `null`, `undefined`, `string`, `number`, `
 An object is plain if it's created by either `{}`, `new Object()`, or `Object.create(null)`.
 
 ##### .iterable(value)
+##### .class(value)
+
+Returns `true` for instances created by a ES2015 class.
+
 ##### .typedArray(value)
 
 
diff --git a/test.js b/test.js
index 7868637..357aa55 100644
--- a/test.js
+++ b/test.js
@@ -273,6 +273,18 @@ test('is.iterable', t => {
 	t.false(m.iterable({}));
 });
 
+test('is.class', t => {
+	class Foo {}
+	const classDeclarations = [
+		Foo,
+		class Bar extends Foo {}
+	];
+
+	for (const x of classDeclarations) {
+		t.true(m.class(x));
+	}
+});
+
 test('is.typedArray', t => {
 	const typedArrays = [
 		new Int8Array(),