Javascript OO，问题通过继承

Question

I've got an issue to fix with some kind of inheritance in JS.

I've set a small jsfiddle to explain, looking at:

V1 http://jsfiddle.net/FFTj4/5/

function Vehicule(name) ...

Here the result are not as expected but easily explained. I'm calling parent constructor with apply which scope the function to the "calling" object where the name is set. So far car and sportcar name are not set in their vehicule prototype so when i ask for the name and going up to vehicule name is undefined.

I fixed it with that:

V2 (uncomment v2 section in the jsfiddle) Well now i'm also "scoping" the getName call to ensure i got my "name". I though it was fixed! So i applied the fix to SportCar also

V3 (uncomment v3 section in the jsfiddle) Well it could not be that easy, now i'm locked SportCar call Car getName, but car is scoped to SportCar so when car "tried" to call Vehicule getName it call SPortCar getName instead, and so on, Maximum call stack size exceeded.

I need to come up with a way to be able to tu call the current object superClass, no matter if called with an apply, and of course keep the scope of the topmost object :/

I've run out of ideas, been on this for almost 2 weeks now.

Thank you !

Answer 1

In line:

Car.prototype.superClass = Vehicule;

You are assinning function, not an instance, so you can't call

this.superClass.prototype.getName();

becouse you have no context. No object was created. You need to do this this way:

this.superClass.prototype.getName.call(this);

Then it should work like you want :)

But, in your code it will not work becouse you are overwriting superClass . You need to use "class" name for this:

Car.prototype.getName.call(this);

Or just don't assign superClass to prototype ;)

Here is a simple explanation of prototypal inheritance. Comments are in polish, but JS is JS ;)