Copy __proto__ successfully in older engines

- If Object.defineProperty is unavailable, fall back to regular assignment
- In getProperty(), return undefined instead of {} when getting __proto__
- Improve style in the __proto__ test

Author: mnespor

index.js

@@ -31,9 +31,9 @@ var isPlainObject = function isPlainObject(obj) {
 	return typeof key === 'undefined' || hasOwn.call(obj, key);
 };
 
-// If name is '__proto__', define it as an own property on target
+// If name is '__proto__', and Object.defineProperty is available, define __proto__ as an own property on target
 var setProperty = function setProperty(target, options) {
-	if (options.name === '__proto__') {
+	if (Object.defineProperty && options.name === '__proto__') {
 		Object.defineProperty(target, options.name, {
 			enumerable: true,
 			configurable: true,
@@ -48,7 +48,7 @@ var setProperty = function setProperty(target, options) {
 // Return a new object instead of __proto__ if '__proto__' is not an own property
 var getProperty = function getProperty(obj, name) {
 	if (name === '__proto__' && !hasOwn.call(obj, name)) {
-		return {};
+		return undefined;
 	}
 
 	return obj[name];

test/index.js

@@ -633,7 +633,6 @@ test('__proto__ is merged as an own property', function (t) {
 	extend(true, target, malicious);
 	t.notOk(target.george);
 	t.ok(Object.prototype.hasOwnProperty.call(target, '__proto__'));
-	var name = '__proto__';
-	t.equal(target[name].george, 1);
+	t.deepEqual(target.__proto__, { george: 1 }); // eslint-disable-line no-proto
 	t.end();
 });