obj.constructor returns top most constructor instead of the immediate parent constructor

Question

just ran into this little confusion while playing around with javascript inheritance.

 function A() {}

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

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

 var x = new C();
 x.construction // -> returns A in chrome console.

I was expecting x.constructor to be C (or even B maybe) but not all the way to A (why even stop at A and not show Object then)

Answer 1

When you replace the prototype object entirely, the original constructor reference is removed with the original prototype object and is instead inherited from the new A(), etc.

function B() {}

console.log(B.prototype.constructor === B); // true

B.prototype = new A();

console.log(B.prototype.constructor === B); // false
console.log(B.prototype.constructor === A); // true

So, you'll have to reset the constructor after setting the prototype:

function A() {}

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

function C() {}
C.prototype = new B();
C.prototype.constructor = C;