Merge pull request #306 from michalkvasnicak/is-plain-object-fix

fix isPlainObject

package.json

@@ -46,6 +46,7 @@
     "babel-core": "^5.6.18",
     "babel-eslint": "^3.1.15",
     "babel-loader": "^5.1.4",
+    "contextify": "^0.1.14",
     "eslint": "^0.23",
     "eslint-config-airbnb": "0.0.6",
     "eslint-plugin-react": "^2.3.0",

src/utils/isPlainObject.js

@@ -1,12 +1,23 @@
+var fnToString = (fn) => Function.prototype.toString.call(fn);
+
 /**
  * @param {any} obj The object to inspect.
  * @returns {boolean} True if the argument appears to be a plain object.
  */
 export default function isPlainObject(obj) {
-  if (!obj) {
+  if (!obj || typeof obj !== 'object') {
     return false;
   }
 
-  return typeof obj === 'object' &&
-         Object.getPrototypeOf(obj) === Object.prototype;
+  var proto = typeof obj.constructor === 'function' ? Object.getPrototypeOf(obj) : Object.prototype;
+
+  if (proto === null) {
+    return true;
+  }
+
+  var constructor = proto.constructor;
+
+  return typeof constructor === 'function'
+    && constructor instanceof constructor
+    && fnToString(constructor) === fnToString(Object);
 }

test/utils/isPlainObject.spec.js

@@ -1,17 +1,24 @@
 import expect from 'expect';
 import isPlainObject from '../../src/utils/isPlainObject';
+import contextify from 'contextify';
 
 describe('isPlainObject', () => {
   it('should return true only if plain object', () => {
     function Test() {
       this.prop = 1;
     }
 
+    const sandbox = contextify();
+    sandbox.run('var fromAnotherRealm = {};');
+
+    expect(isPlainObject(sandbox.fromAnotherRealm)).toBe(true);
     expect(isPlainObject(new Test())).toBe(false);
     expect(isPlainObject(new Date())).toBe(false);
     expect(isPlainObject([1, 2, 3])).toBe(false);
     expect(isPlainObject(null)).toBe(false);
     expect(isPlainObject()).toBe(false);
     expect(isPlainObject({ 'x': 1, 'y': 2 })).toBe(true);
+
+    sandbox.dispose();
   });
 });