Instanceof equivalent for Object.create and prototype chains

Consider such an object with a prototype chain:

var A = {};
var B = Object.create(A);
var C = Object.create(B);

How to check in runtime if C has A in its prototype chain?

instanceof doesn't fit as it's designed to work with constructor functions, which I'm not using here.

Solution

My answer will be short…

You could use the isPrototypeOf method, which will be present in case your object inherits from the Object prototype, like your example.

example:

A.isPrototypeOf(C) // true
B.isPrototypeOf(C) // true
Array.prototype.isPrototypeOf(C) // false