How to check if a Javascript Class inherits another (without creating an obj)?

Question

Eg:

function A(){}
function B(){}
B.prototype = new A();

How can I check if the class B inherits class A?

Answer 1

You can test direct inheritance with

B.prototype.constructor === A

To test indirect inheritance, you may use:

B.prototype instanceof A

(this second solution was first given by Nirvana Tikku)