Support Object.create(null) as plain object (#23)

Ref #12 babel/babel#11855 (comment)

README.md

@@ -1,6 +1,6 @@
 # is-plain-object [![NPM version](https://img.shields.io/npm/v/is-plain-object.svg?style=flat)](https://www.npmjs.com/package/is-plain-object) [![NPM monthly downloads](https://img.shields.io/npm/dm/is-plain-object.svg?style=flat)](https://npmjs.org/package/is-plain-object) [![NPM total downloads](https://img.shields.io/npm/dt/is-plain-object.svg?style=flat)](https://npmjs.org/package/is-plain-object) [![Linux Build Status](https://img.shields.io/travis/jonschlinkert/is-plain-object.svg?style=flat&label=Travis)](https://travis-ci.org/jonschlinkert/is-plain-object)
 
-> Returns true if an object was created by the `Object` constructor.
+> Returns true if an object was created by the `Object` constructor, or Object.create(null).
 
 Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support.
 
@@ -116,4 +116,4 @@ Released under the [MIT License](LICENSE).
 
 ***
 
-_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.8.0, on April 28, 2019._
+_This file was generated by [verb-generate-readme](https://github.com/verbose/verb-generate-readme), v0.8.0, on April 28, 2019._

index.js

@@ -8,8 +8,9 @@
 import isObject from 'isobject';
 
 function isObjectObject(o) {
+  var type = Object.prototype.toString.call(o)
   return isObject(o) === true
-    && Object.prototype.toString.call(o) === '[object Object]';
+    && (type === '[object Object]' || type === '[object Null]');
 }
 
 export default function isPlainObject(o) {
@@ -19,7 +20,7 @@ export default function isPlainObject(o) {
 
   // If has modified constructor
   ctor = o.constructor;
-  if (typeof ctor !== 'function') return false;
+  if (ctor === undefined) return true;
 
   // If has modified prototype
   prot = ctor.prototype;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "is-plain-object",
-  "description": "Returns true if an object was created by the `Object` constructor.",
+  "description": "Returns true if an object was created by the `Object` constructor, or Object.create(null).",
   "version": "3.0.1",
   "homepage": "https://github.com/jonschlinkert/is-plain-object",
   "author": "Jon Schlinkert (https://github.com/jonschlinkert)",

test/browser-iframe.html

@@ -12,7 +12,8 @@
   Object.create({}),
   Object.create(Object.prototype),
   {foo: 'bar'},
-  {}
+  {},
+  Object.create(null)
 ];
 
 // Should return false with isPlainObject()
@@ -23,8 +24,7 @@
   ['foo', 'bar'],
   [],
   new Foo,
-  null,
-  Object.create(null)
+  null
 ];
 
 </script>

test/server.js

@@ -14,6 +14,7 @@ describe('Same-Realm Server Tests', function() {
     assert(isPlainObject(Object.create(Object.prototype)));
     assert(isPlainObject({foo: 'bar'}));
     assert(isPlainObject({}));
+    assert(isPlainObject(Object.create(null)));
   });
 
   it('should return `false` if the object is not created by the `Object` constructor.', function() {
@@ -26,6 +27,5 @@ describe('Same-Realm Server Tests', function() {
     assert(!isPlainObject([]));
     assert(!isPlainObject(new Foo));
     assert(!isPlainObject(null));
-    assert(!isPlainObject(Object.create(null)));
   });
 });