Tests for ES6 class constructor return values On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". Base class PASS (new BaseNoReturn) instanceof BaseNoReturn is true PASS (new BaseReturnImplicit) instanceof BaseReturnImplicit is true PASS (new BaseReturnImplicit) !== undefined is true PASS (new BaseReturnUndefined) instanceof BaseReturnUndefined is true PASS (new BaseReturnUndefined) !== undefined is true PASS (new BaseReturnThis) instanceof BaseReturnThis is true PASS (new BaseReturnObject) instanceof BaseReturnObject is false PASS typeof (new BaseReturnObject) === "object" is true PASS (new BaseReturnObject2) instanceof BaseReturnObject is false PASS (new BaseReturnObject2) === globalVariable is true PASS (new BaseReturnString) instanceof BaseReturnString is true PASS typeof (new BaseReturnString) !== "string" is true PASS (new BaseReturnNumber) instanceof BaseReturnNumber is true PASS typeof (new BaseReturnNumber) !== "number" is true PASS (new BaseReturnNull) instanceof BaseReturnNull is true PASS (new BaseReturnNull) !== null is true PASS (new BaseReturnSymbol) instanceof BaseReturnSymbol is true PASS (new BaseReturnSymbol) !== globalSymbol is true PASS (new BaseThrow) threw exception Thrown Exception String. Function constructor (non-class) PASS (new FunctionNoReturn) instanceof FunctionNoReturn is true PASS (new FunctionReturnImplicit) instanceof FunctionReturnImplicit is true PASS (new FunctionReturnImplicit) !== undefined is true PASS (new FunctionReturnUndefined) instanceof FunctionReturnUndefined is true PASS (new FunctionReturnUndefined) !== undefined is true PASS (new FunctionReturnThis) instanceof FunctionReturnThis is true PASS (new FunctionReturnObject) instanceof FunctionReturnObject is false PASS typeof (new FunctionReturnObject) === "object" is true PASS (new FunctionReturnObject2) instanceof FunctionReturnObject is false PASS (new FunctionReturnObject2) === globalVariable is true PASS (new FunctionReturnString) instanceof FunctionReturnString is true PASS typeof (new FunctionReturnString) !== "string" is true PASS (new FunctionReturnNumber) instanceof FunctionReturnNumber is true PASS typeof (new FunctionReturnNumber) !== "number" is true PASS (new FunctionReturnNull) instanceof FunctionReturnNull is true PASS (new FunctionReturnNull) !== null is true PASS (new FunctionReturnSymbol) instanceof FunctionReturnSymbol is true PASS (new FunctionReturnSymbol) !== globalSymbol is true PASS (new FunctionThrow) threw exception Thrown Exception String. Derived class calling super() PASS (new DerivedNoReturn) instanceof DerivedNoReturn is true PASS (new DerivedReturnImplicit) instanceof DerivedReturnImplicit is true PASS (new DerivedReturnImplicit) !== undefined is true PASS (new DerivedReturnUndefined) instanceof DerivedReturnUndefined is true PASS (new DerivedReturnUndefined) !== undefined is true PASS (new DerivedReturnThis) instanceof DerivedReturnThis is true PASS (new DerivedReturnObject) instanceof DerivedReturnObject is false PASS typeof (new DerivedReturnObject) === "object" is true PASS (new DerivedReturnObject2) instanceof DerivedReturnObject2 is false PASS (new DerivedReturnObject2) === globalVariable is true PASS (new DerivedReturnString) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedReturnNumber) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedReturnNull) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedReturnSymbol) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedThrow) threw exception Thrown Exception String. Derived class not calling super() PASS (new DerivedNoSuperNoReturn) threw exception ReferenceError: Must call super constructor in derived class before accessing 'this' or returning from derived constructor. PASS (new DerivedNoSuperReturnImplicit) threw exception ReferenceError: DerivedNoSuperReturnImplicit is not defined. PASS (new DerivedNoSuperReturnUndefined) threw exception ReferenceError: Must call super constructor in derived class before accessing 'this' or returning from derived constructor. PASS (new DerivedNoSuperReturnThis) threw exception ReferenceError: Must call super constructor in derived class before accessing 'this' or returning from derived constructor. PASS (new DerivedNoSuperReturnObject) did not throw exception. PASS (new DerivedNoSuperReturnObject2) did not throw exception. PASS (new DerivedNoSuperReturnString) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedNoSuperReturnNumber) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedNoSuperReturnNull) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedNoSuperReturnSymbol) threw exception TypeError: Derived constructors may only return object or undefined. PASS (new DerivedNoSuperThrow) threw exception Thrown Exception String. Derived class with default constructor and base class returning different values PASS (new DerivedDefaultConstructorWithBaseNoReturn) instanceof DerivedDefaultConstructorWithBaseNoReturn is true PASS (new DerivedDefaultConstructorWithBaseReturnImplicit) instanceof DerivedDefaultConstructorWithBaseReturnImplicit is true PASS (new DerivedDefaultConstructorWithBaseReturnUndefined) instanceof DerivedDefaultConstructorWithBaseReturnUndefined is true PASS (new DerivedDefaultConstructorWithBaseReturnObject) instanceof DerivedDefaultConstructorWithBaseReturnObject is false PASS typeof (new DerivedDefaultConstructorWithBaseReturnObject) === "object" is true PASS (new DerivedDefaultConstructorWithBaseReturnObject2) instanceof DerivedDefaultConstructorWithBaseReturnObject2 is false PASS (new DerivedDefaultConstructorWithBaseReturnObject2) === globalVariable is true PASS (new DerivedDefaultConstructorWithBaseReturnThis) instanceof DerivedDefaultConstructorWithBaseReturnThis is true PASS (new DerivedDefaultConstructorWithBaseReturnString) instanceof DerivedDefaultConstructorWithBaseReturnString is true PASS (new DerivedDefaultConstructorWithBaseReturnNumber) instanceof DerivedDefaultConstructorWithBaseReturnNumber is true PASS (new DerivedDefaultConstructorWithBaseReturnNull) instanceof DerivedDefaultConstructorWithBaseReturnNull is true PASS (new DerivedDefaultConstructorWithBaseReturnSymbol) instanceof DerivedDefaultConstructorWithBaseReturnSymbol is true PASS (new DerivedDefaultConstructorWithBaseThrow) threw exception Thrown Exception String. PASS successfullyParsed is true TEST COMPLETE