Re: Newbie trying to understand object oriented programming

From	Joao Rodrigues <jr@none.com>
Newsgroups	comp.lang.javascript
Subject	Re: Newbie trying to understand object oriented programming
Date	2016-02-06 11:56 -0200
Organization	Aioe.org NNTP Server
Message-ID	<n94u26$5pp$1@gioia.aioe.org> (permalink)
References	<664696a0-3ce3-484c-aeaf-2fdf45781bb4@googlegroups.com>

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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

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Thread

Newbie trying to understand object oriented programming bit-naughty@hotmail.com - 2016-02-05 06:55 -0800
  Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-05 18:56 +0000
  Re: Newbie trying to understand object oriented programming Tim Slattery <tim@risingdove.com> - 2016-02-05 14:07 -0500
  Re: Newbie trying to understand object oriented programming Aleksandro <aleksandro@gmx.com> - 2016-02-05 17:34 -0300
    Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-05 19:10 -0800
      Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-06 08:33 +0000
        Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-06 08:24 -0800
          Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-06 18:48 +0000
            Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-06 12:28 -0800
              Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-06 21:01 +0000
                Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-07 15:23 -0800
                Re: Newbie trying to understand object oriented programming Aleksandro <aleksandro@gmx.com> - 2016-02-08 11:45 -0300
            Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-08 13:39 -0800
              Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-11 08:09 -0800
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-11 12:22 -0800
                Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-12 11:09 +0000
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-12 13:34 -0800
                Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-13 14:40 +0000
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-14 10:18 -0800
                Re: Newbie trying to understand object oriented programming Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-14 21:27 +0100
                Re: Newbie trying to understand object oriented programming "J. Clarke" <j.clarke.873638@gmail.com> - 2016-05-14 10:13 -0400
                Re: Newbie trying to understand object oriented programming Tim Streater <timstreater@greenbee.net> - 2016-05-14 16:47 +0100
                Re: Newbie trying to understand object oriented programming "J. Clarke" <j.clarke.873638@gmail.com> - 2016-05-15 07:05 -0400
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-14 10:08 -0700
                Re: Newbie trying to understand object oriented programming "J. Clarke" <j.clarke.873638@gmail.com> - 2016-05-15 07:02 -0400
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-15 13:11 -0700
                Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-05-15 17:03 +0100
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-15 13:20 -0700
                Re: Newbie trying to understand object oriented programming Gene Wirchenko <genew@telus.net> - 2016-05-16 11:55 -0700
                Re: Newbie trying to understand object oriented programming Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-05-16 21:39 +0200
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-17 07:30 -0700
                Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-05-17 15:34 +0100
                Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-13 17:50 -0800
                Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-14 11:15 +0000
                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-14 11:03 -0800
                Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-15 20:18 +0000
                Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-13 16:54 -0800
  Re: Newbie trying to understand object oriented programming Danny <dann90038@gmail.com> - 2016-02-05 15:00 -0800
  Re: Newbie trying to understand object oriented programming RobG <rgqld@iinet.net.au> - 2016-02-06 17:18 +1000
    Re: Newbie trying to understand object oriented programming Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-06 16:01 +0100
    Re: Newbie trying to understand object oriented programming bit-naughty@hotmail.com - 2016-02-07 04:47 -0800
      Re: Newbie trying to understand object oriented programming Tim Streater <timstreater@greenbee.net> - 2016-02-07 13:16 +0000
      Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-07 17:29 +0000
        Re: Newbie trying to understand object oriented programming bit-naughty@hotmail.com - 2016-02-08 08:53 -0800
          Re: Newbie trying to understand object oriented programming Tim Streater <timstreater@greenbee.net> - 2016-02-08 17:33 +0000
  Re: Newbie trying to understand object oriented programming Joao Rodrigues <jr@none.com> - 2016-02-06 11:56 -0200

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