Path: csiph.com!aioe.org!.POSTED!not-for-mail
From: Joao Rodrigues <jr@none.com>
Newsgroups: comp.lang.javascript
Subject: Re: Newbie trying to understand object oriented programming
Date: Sat, 6 Feb 2016 11:56:22 -0200
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bit-naughty@hotmail.com wrote:
> Hi, OK, I've read about and tried to understand OOP for a long time
> now, but I don't think I really get it.

In this case, I'd suggest reading this article in MDN:
<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Introduction_to_Object-Oriented_JavaScript>


> This question just popped
> into my head while mulling the whole thing over:
>
> "this" means *that one*, right? Like, it's a cookie cutter.....?
>
> Then what about this?:
>
> if I have:
>
> function vegetables() { this.colour="brown"; }

There is a convention about constructor functions that their names 
should start with an upper case letter. Then you should write:

function Vegetables() {
   this.colour = "brown";
}

>
> and I do both a var potatoes = new vegetables() ;
>
> AND a var tomatoes = new vegetables();
>
>
> Then BOTH potatoes.colour will be "brown" *AND* tomatoes.colour will
> be "brown", right.....??!!!

Yes, because all instances of Vegetables will have the property 'colour' 
with the same value ('brown').

You should have declared Vegetables() as:

function Vegetables(colour) {
   this.colour = colour;
}

var tomato = new Vegetables('red');
console.log(tomato.colour); // red

var potato = new Vegetables('brown');
console.log(potato.colour); // brown

Douglas Crockford once wrote: "JavaScript is a prototypal language, but 
it has a *new* operator that tries to make it look sort of like a 
classical language. That tends to confuse programmers, leading to some 
problematic programming patterns."
<http://yuiblog.com/blog/2006/11/13/javascript-we-hardly-new-ya/>

It would be simpler if you used:

var vegetables = {
   tomatoes: {
     colour: 'red'
   },
   potatoes: {
     colour: 'brown'
   }
};

It is even simpler if you need to add properties to vegetables:

vegetables.bananas = {colour: 'yellow'};

var tomato = vegetables.tomatoes;
console.log(tomato.colour); // red

var potato = vegetables.potatoes;
console.log(potato.colour); // brown

var banana = vegetables.bananas;
console.log(banana.colour); //yellow


ECMAScript 2015 (aka ES6) introduced "class", which is a syntactical 
sugar over JavaScript's existing prototype-based inheritance. See:
<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes>

class Vegetables {
   constructor(colour) {
     this.colour = colour;
   }
}

var potatoes = new Vegetables('brown');
console.log(potatoes.colour); // brown


--
Joao Rodrigues