Question about functional OOP style in JavaScript

Question

I prefer to use functional OOP style for my code (similar to the module pattern) because it helps me to avoid the "new" keyword and all problems with the scope of "this" keyword in callbacks.

But I've run into a few minor issues with it. I would like to use the following code to create a class.

namespace.myClass = function(){
  var self = {},
      somePrivateVar1;

  // initialization code that would call
  // private or public methods
  privateMethod();
  self.publicMethod(); // sorry, error here

  function privateMethod(){}

  self.publicMethod = function(){};

  return self;
}

The problem is that I can't call public methods from my initialization code, as these functions are not defined yet. The obvious solution would be to create an init method, and call it before "return self" line. But maybe you know a more elegant solution?

Also, how do you usually handle inheritance with this pattern? I use the following code, butI would like to hear your ideas and suggestions.

namespace.myClass2 = function(){
  var self = namespace.parentClass(),
      somePrivateVar1;            

  var superMethod = self.someMethod;
  self.someMethod = function(){
    // example shows how to overwrite parent methods
    superMethod();
  };

  return self;
}

Edit. For those who asked what are the reasons for choosing this style of OOP, you can look into following questions:

• http://stackoverflow.com/questions/1557386/prototypal-vs-functional-oop-in-javascript
• http://stackoverflow.com/questions/383402/is-javascript-s-new-keyword-considered-harmful

Answer 1

Several questions occur to me, such as why you want to avoid the new operator, and why you want to call functions before they are defined. However, leaving those aside, how about something more like the following?

namespace.myClass = function(){
  var somePrivateVar1;
  var self = {};

  // initialization code that would call
  // private or public methods
  privateMethod();
  publicMethod();

  function privateMethod(){}
  function publicMethod(){}

  self.publicMethod = publicMethod;
  return self;
}

Answer 2

I agree with almost every comment or answer provided so far, but to take Tim's answer one step further - he questioned why you'd want to call a method before it was defined, but offered a solution anyway, whereas I'd suggest you shouldn't call before defining (I don't know of any language where calling a method prior to defining it or at least declaring it is considered good practice), so how about:

namespace.myClass = function(){  
  //declare private vars (and self) first
  var self = {},  
      somePrivateVar1;  

  //then declare private methods
  function privateMethod(){}  

  //then public/privileged methods
  self.publicMethod = function(){};  

  // THEN (and only then) add your 
  // initialization code that would call  
  // private or public methods  
  privateMethod();  
  self.publicMethod(); // no error any more

  //then return the new object
  return self;  
} 

Is there a particular reason why this would not work for you?

Answer 3

This is the solution I mentioned in the question. Your comments are welcome.

namespace.myClass = function(){
  var self = {},
      somePrivateVar1;

  function init(){
    privateMethod();
    self.publicMethod();
  }

  function privateMethod(){}
  self.publicMethod = function(){};

  init();
  return self;
}

Answer 4

Hi, there,

You can use Zet.js library which will help you with declaring classes in the way you want.