Javascript Prototypal Inheritance?

Question

I\'been doing some inheritance in js in order to understand it better, and I found something that confuses me.

I know that when you call an \'constructor function\' with

Answer 1

You cannot change an object's prototype once it's been instantiated with new.

In your example above, lines like

fido.prototype = new KillerDog();

simply creates a new attribute named prototype on the object fido, and sets that attribute to a new KillerDog object. It's no different than

fido.foo = new KillerDog();

As your code stands...

// Doesn't work because objects can't be changed via their constructors
fido.deathBite();

// Does work, because objects can be changed dynamically, 
// and Javascript won't complain when you use prototype 
//as an object attribute name
fido.prototype.deathBite();

The special prototype behavior applies only to constructors in javascript, where constructors are functions that will be called with new.