x instanceof f: true+− x instanceof b: true+− y instanceof f: true+− y instanceof b: true+− +− Changing prototype+− +− x instanceof f: false+− x instanceof b: false+− y instanceof f: false+− y instanceof b: false+− Bound function prototype+− +− f.hasOwnProperty('prototype'): true+− b.hasOwnProperty('prototype'): false+−