The Constructor Of Object.prototype

In JavaScript, every object inherits its properties and methods from a specific prototype, where prototypes are objects. The inheritance forms a prototype chain where (Object.proto

Solution 1:

From "this and Object Prototypes" book of "You don't know JS" series by Kyle Simpsion

functionFoo() {
    // ...
}

Foo.prototype.constructor === Foo; // truevar a = newFoo();
a.constructor === Foo; // true

The Foo.prototype object by default (at declaration time on line 1 of the snippet!) gets a public, non-enumerable (see Chapter 3) property called .constructor, and this property is a reference back to the function (Foo in this case) that the object is associated with. Moreover, we see that object a created by the "constructor" call new Foo() seems to also have a property on it called .constructor which similarly points to "the function which created it".

Note: This is not actually true. a has no .constructor property on it, and though a.constructor does in fact resolve to the Foo function, "constructor" does not actually mean "was constructed by", as it appears. We'll explain this strangeness shortly.

...

"Objects in JavaScript have an internal property, denoted in the specification as [[Prototype]], which is simply a reference to another object.".

So, Object.prototype itself is not an object. As to your specific question about instanceof:

var a = newFunction();
a.prototypeinstanceofObject; //truevar b = newString();
b.prototypeinstanceofObject; //false