Javascript Class Inheritance For Functions

Question

I have set up a base class as standard:

MyBase = function() {
    this.m_Stuff = 0; // etc
};
MyBase.prototype.MySuperFunction = function (arg1) {
    alert("Hello" + arg1);
};

Next I set up another class that inherits MyBase

MyChild = function () {
    MyBase.call(this);
    this.m_OtherStuff = 1; // etc
};
MyChild.prototype = new MyBase(); // innherit

But then (and this is the bit I dont know how to do) I want to override MyBase's MySuperFunction with a better one, but calling the base class function in the process:

MyChild.prototype.MySuperFunction = function (arg1, arg2) {
    MyBase.MySuperFunction(arg1); // THIS LINE IS THE LINE I DONT KNOW HOW TO DO
    alert("You is a " + arg2 + "'th level idiot");
};

Its a child class that wants to override is base class function, but wants to call the base class function in the new improved definition.

Is this possible, and if so, how can it be done?

just to clarify, so are you saying MyBase.prototype.MySuperFunction needs to alert "You is a " + arg2 + "'th level idiot" or you are just trying to invoke it in the context of the child class method? — chrisvillanueva
– chrisvillanueva, Commented Jun 6, 2013 at 13:23
I want my child class to call the base class' function before adding it's own amendment. — Rewind
– Rewind, Commented Jun 6, 2013 at 14:03

Community · Accepted Answer · 2017-05-23 10:28:26Z

8

It's similar to the call in your inherited constructor. You can access the "super" method still on MyBase.prototype.MySuperFunction (where you assigned it), so use:

MyBase.prototype.MySuperFunction.call(this, arg1);

For a more dynamic approach you even might use Object.getPrototypeOf to get the prototype, but watch out that it works with dynamic inheritance. And if you have many methods that need to call their parent, it can be helpful to alias MyBase.prototype as a super variable which is accessible to all functions on the Child prototype object (see this answer for an example)).

edited May 23, 2017 at 10:28

CommunityBot

11 silver badge

answered Jun 6, 2013 at 13:18

Bergi

671k162 gold badges1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Rewind Over a year ago

So to clarify, you are saying my child's function will be MyChild.prototype.MySuperFunction = function (arg1, arg2) {MyBase.prototype.MySuperFunction.call(this, arg1); alert("You is a " + arg2 + "'th level idiot"); };

abbood Over a year ago

@Bergi is there a way to call this prototype thing within the original declaration of the function/object? this gist provides an example of what i'm talking about

Bergi Over a year ago

No, prototype properties have to be declared outside the constructor function

abbood Over a year ago

@Bergi!!!!!!!! that's incredibly ugly isn't it? I mean I would like to know that everything related to a defined "object" is encapsulated within those braces.. otherwise anyone can add all sortsa stuff anywhere within 100 js files in a large project.. is there a way to address this?

Bergi Over a year ago

Yes, it's called module pattern - basically wrap constructor and prototype assignments in an IEFE. See also this question. Btw, you don't need to shout at me :-)

|

pvnarula · Accepted Answer · 2013-06-06 14:17:53Z

3

Please apply the following:-

MyBase.prototype.MySuperFunction.call(this, arg1);

edited Jun 6, 2013 at 14:17

answered Jun 6, 2013 at 13:17

pvnarula

2,84120 silver badges22 bronze badges

1 Comment

Rewind Over a year ago

So to clarify, you are saying my child's function will be MyChild.prototype.MySuperFunction = function (arg1, arg2) {MyBase.prototype.MySuperFunction.call(this, arg1); alert("You is a " + arg2 + "'th level idiot"); }; Also, when I set up an instance elsewhere; var mychild = new MyChild(); I would then call the CHILD'S version of the function with: mychild.MySuperFunction("Dave", "7");

Collectives™ on Stack Overflow

Javascript Class Inheritance For Functions

2 Answers 2

8 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

8 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related