子方法无法识别父方法-JavaScript原型继承

Question

--- apparently I did a mistake and the following code DOES work... ---

I am new to JavaScript and prototype inheritance. I come from a class-based inheritance language background.

I'm trying to create a parent object that does some stuff in it's prototype's methods. It has a certain method (doSomething) that inside it calls another method (doNestedSomething).

function Parent (num)
{
    this.num = num;
}

Parent.prototype.doSomething = function()
{
    this.doNestedSomething();
};

Parent.prototype.doNestedSomething = function()
{
    this.num++;
    console.log(this.num);
};

Then I want to create a child that inherits from the super, and overrides the certain method.

function Child (num, st)
{
    this.st = st;

    Parent.call(this, num);
}

Child.prototype = Object.create(Parent.prototype);

Child.prototype.doSomething = function()
{
    this.st += " " + this.st;
    console.log(this.st);

    Parent.prototype.doSomething.call(this);
};

The problem is, that once it calls the super's doSomething method, inside it the doNestedSomething method somehow does not exist.

var child = new Child(0, "kawaii");
child.doSomething(); //Uncaught TypeError: this.doNestedSomething is not a function

I think I'm doing something wrong. I looked around here about inheritance and prototype and tried to implement it as depicted there.
But I can not find any information on how a child can call a super method, when the super method calls some other super method...

I looked at John Resig's way to implement inheritance, but still do not see there an example for a child indirectly calling a parent method that does not exist...

Answer 1

I've just tested your exemple and it works well,

For :

var child = new Child(0, "kawaii");
child.doSomething();
child.doSomething();
child.doSomething();

It output without exception :

kawaii kawaii
1
kawaii kawaii kawaii kawaii
2
kawaii kawaii kawaii kawaii kawaii kawaii kawaii kawaii
3

Fiddle : https://jsfiddle.net/uwb7omx3/

Tested on chrome 42