Fixes #13571. jQuery.isPlainObject 1.9.x compatibility

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/src/core.js b/src/core.js
index cae3a90e3..39e68c4fc 100644
--- a/src/core.js
+++ b/src/core.js
@@ -422,8 +422,11 @@ jQuery.extend({
 	},
 
 	isPlainObject: function( obj ) {
+		var key;
 		// Not plain objects:
 		// - Any object or value whose internal [[Class]] property is not "[object Object]"
+		//   ...Unless it was a constructor, whose prototype property was paved over by
+		//   by a plain object at its declaration. #13571
 		// - DOM nodes
 		// - window
 		if ( jQuery.type( obj ) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {
@@ -442,9 +445,11 @@ jQuery.extend({
 			return false;
 		}
 
-		// If the function hasn't returned already, we're confident that
-		// |obj| is a plain object, created by {} or constructed with new Object
-		return true;
+		// Own properties are enumerated firstly, so to speed up,
+		// if last one is own, then all properties are own.
+		for ( key in obj ) {}
+
+		return key === undefined || core_hasOwn.call( obj, key );
 	},
 
 	isEmptyObject: function( obj ) {