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

I do not think Simon meant B.prototype = new A() in his question, because this is certainly not the way to chain prototypes in JavaScript.

Assuming B extends A, use Object.prototype.isPrototypeOf.call(A.prototype, B.prototype)