javascript Function.prototype问题

Question

I started learning JavaScript and have below question:

 var f = function foo() {} Console.log(f.__proto__ === Function.prototype) //true Console.log(f.__proto__ instance of Function) //false 

Why 3rd statement using instanceof returns false. My understanding is RHS of instance consults prototype of passed class and then match it in object or its proto. Please let me know what I am missing here? referred this for implementation of instance-of.

Answer 1

referred this for implementation of instance-of

Well, that's simply a wrong implementation. The instanceof operator does not match the object itself, only its prototypes, against the .prototype of the constructor. Your

x instanceof Function

is equivalent to

Function.prototype.isPrototypeOf(x)

which for f.__proto__ (ie Function.prototype ) does not hold - it is not the prototype of itself.