+ isPlainObject: function( obj ) {
+ if ( toString.call(obj) !== "[object Object]" || typeof obj.nodeType === "number" ) {
+ return false;
+ }
+
+ // not own constructor property must be Object
+ if ( obj.constructor
+ && !hasOwnProperty.call(obj, "constructor")
+ && !hasOwnProperty.call(obj.constructor.prototype, "isPrototypeOf") ) {
+ return false;
+ }
+
+ //own properties are iterated firstly,
+ //so to speed up, we can test last one if it is own or not
+
+ var key;
+ for ( key in obj ) {}
+
+ return key === undefined || hasOwnProperty.call( obj, key );