JavaScript - Javascript | Prototypal Inheritance Vs. Classical Inheritance

Hi, I would like to know which is the best approach when trying inheritance with js - module pattern. In the example below, I want that parent.hi() be fired from child:


Code:

var parent = function(){
    return{
        hi: function(){
            console.info('hi');
        }
    }
}();

var child = function(){
    

    return{
        bye: function(){
            console.info('bye');
        },
        hi: function(){//look he 
            
            parent.hi();    

        }   
    }
}();


child.hi();

Is there a better way to do this ?

Thanks in advance

I'm having a javascript problem with nested elements. Consider an example in which you have two nested elements with element 2 being inside of element 1 and only element 1 has an onmouseout event handler.

<div style="position:relative;border:1px solid red;width:300px;height:300px" onmouseout="alert('whatever')"> //element 1
<div style="position:absolute;border:1px solid blue;left:50%;top:50%;margin-left:-50px;margin-top:-50px;width:100px;height:100px">//element 2
</div>
</div>

The 2 problems here are as follows:

1- Moving the mouse pointer over element 2 from element 1 causes a onmouseout with element 1. But this is a minor problem.
2- Moving the mouse pointer from element 2 back to element 1 causes a mouseout with ,I believe, element 2 even though there is no onmouseout event handler here. This is a major problem.

Is problem #2 due to possibly an automatic inheritance of the onmouseover handler from element 1 onto element 2 OR is it the result of event capturing or what else? I can't tell either way. If it's due to inheritance how do you stop this from taking place? The strange thing is that tutorials give this kind of scenario with element 2 inside of element 1 with both elements having the same event handler but they don't say what happens in this case with just one element having a specific event handler. Thank you.

Hi!

This is probably a classic inheritance thing...

I have two objects, C1 and C2. Both contains a callback method named 'callback'. Now, if I let C2 inherit from C1, then C1's 'callback' gets overridden by C2's. The problem is I still want C1's methods to access their own 'callback' method.

Is this possible, and is it "valid"? Am I headed down disaster lane here? Should I re-think and refactor?


Example:

Code:

function C1 () {};

C1.prototype.callback = function () {
	console.log('c1 called');
};

C1.prototype.call = function () {
	//do stuff
	this.callback();
};

function C2 () {};

C2.prototype = new C1();

C2.prototype.callback = function () {
	console.log('c2 called');
};


var obj = new C2();
obj.call();

Output:
c2 called Regards

Don

I posted this once, but it disappeared, and I have no notifications that I did anything wrong. I read the rules before posting and wasn't breaking any so I am not sure why it disappeared but here goes again.

I am trying to learn Javascript (particularly OOP) from a series of screencasts by Douglas Crockford. I have developed a theoretical "game" to build to illustrate it to myself better, and learn by example.

I must be misunderstanding how inheritance works, because my code is not producing the results I thought it would.

Here is what I have, followed by an explanation of my understanding.
Code:

$(function() {

function object(o) {
	function Funct() {}
	Funct.prototype = o;
	return new Funct();
}


soldier = {
      pointsCost: 0,
      movement: "1 Infantry Block",
      validTargets: {},
      weapons: {
			"Main Weapon": {
				"Weapon Type": "M4 Carbine",
				"Fire Range": 12
			},
			"Secondary Weapon": {
				"Weapon Type": "JCP .45",
				"Fire Range": 3
			}
		}
};

var rifleman = object(soldier); 
rifleman.pointsCost += 10;
rifleman.validTargets.target1 = "Infantry"
rifleman.weapons["Secondary Weapon"]["Weapon Type"] = "";
rifleman.weapons["Secondary Weapon"]["Fire Range"] = "";


var heavyGunner = object(soldier);
heavyGunner.pointsCost += 20;
heavyGunner.validTargets.target1 = "Infantry";
heavyGunner.validTargets.target2 = "Light Armor";
heavyGunner.weapons["Main Weapon"]["Weapon Type"] = "SAW M249";
heavyGunner.weapons["Main Weapon"]["Fire Range"] = 12;
heavyGunner.weapons["Secondary Weapon"]["Weapon Type"] = "";
heavyGunner.weapons["Secondary Weapon"]["Fire Range"] = "";
 
var sniper = object(soldier);
sniper.pointsCost += 30;
sniper.validTargets.target1 = "Infantry";
sniper.weapons["Main Weapon"]["Weapon Type"] = "Savage .308";
sniper.weapons["Main Weapon"]["Fire Range"] = 20;
sniper.weapons["Secondary Weapon"]["Weapon Type"] = "JCP .45";
sniper.weapons["Secondary Weapon"]["Fire Range"] = 3;

 
var demolitions = object(soldier);
demolitions.pointsCost += 30;
demolitions.validTargets.target1 = "Infantry";
demolitions.validTargets.target2 = "Light Armor";
demolitions.validTargets.target3 = "Artilery";
demolitions.validTargets.target4 = "Structures";
demolitions.weapons["Main Weapon"]["Weapon Type"] = "SMAW MK153";
demolitions.weapons["Main Weapon"]["Fire Range"] = 16;
demolitions.weapons["Secondary Weapon"]["Weapon Type"] = "M1014 Combat Shotgun";
demolitions.weapons["Secondary Weapon"]["Fire Range"] = 1; 


var infantry = { 

    rifleman: rifleman, 
    
    heavyGunner: heavyGunner, 
     
    sniper: sniper, 
     
    demolitions: demolitions 
 
};



console.log(infantry);

});

I start by creating an object function that accepts an object passed in, and sets it to the prototype of a constructor (that would allow me to create a new object linked to, and inheriting from, the initial passed in object)

I initialized a solider object literal, and pass that into the object function while creating 4 new objects (rifleman, heavyGunner, sniper, demolitions)
These four should inherit from and customize upon the soldier object.

The way I understood inheritance is that the new objects (example. rifleman) would inherit properties from the old object (i.e. soldier) and change or add properties, affecting only the new (rifleman) object but not changing the old(solider) object.

this works ok somewhat in my example, until it comes to nested objects.
In the above example I have objects as values for some Object's properties. (i.e. validTargets and weapons) When I change or add these, all of the new objects seem to inherit the last declarations, from demolitions, as if demolitions is actually changing that part of the soldier object so that the other's inherit those properties.

From my viewpoint, I expected these values to not be changed and that the 4 infantry types had no link to each other, but only to the soldier object.

I apparently misunderstood something, or coded something wrong.

Some minor notes:
-I will be updating most of the "string" values to be objects, so for instance, the validTargets value of "Infantry" would actually be the infantry object, stating that any of the 4 solider types would be a valid target.
- I intend to create weapons as their own viable objects in the future, and pass those objects instead of "strings"
- I intend to extend this (once this is working) to create an armor object that contains armor type units, similar in structure to the infantry object.
- If I can get this all to work, I may make this into a "simple" dice style battle game. but that is way off, I just want to get this nesting of objects to work with inheritance for now.

Thanks in advance for any help you can provide.
Here is a link to the "live" example. (not much different there except if you have firebug you can see the console.log method showing the objects, and how they are inheriting in properly from my POV.)

Link to Live example...


Blue

Hello,
I am new with Javascript and running into this problem that I don't understand.

I define a base class that only contains an array "elements", and a derived class that contains nothing more (for simplicity):

Code:

  function baseClass() {
     this.elements = new Array;
  }

  function derivedClass() {
  }
  derivedClass.prototype = new baseClass;

Then I create two instances of the derived class, and add two elements in each:

Code:

   a = new derivedClass();
   a.elements.push("A");
   a.elements.push("B");

   b = new derivedClass();
   b.elements.push("C");
   b.elements.push("D");

When I examine the contents of these arrays, I see that both a.elements and b.elements contain {"A","B","C","D"} ! I.e. as if the two arrays are in fact the same array! But these are two separate instances of the class, I expect two separate arrays.

Note that if instead I use the base class:

Code:

   a = new baseClass();
   a.elements.push("A");
   a.elements.push("B");

   b = new baseClass();
   b.elements.push("C");
   b.elements.push("D");

then I get a.elements = {"A","B"} and b.elements = {"C","D"}, as I would expect.

Could someone explain to me the problem with using the derived class?

Thank you,
Stephanos

Hello! I am trying to find a script that allows you to open multiple browser tabs and then close each of those tabs, either one by one or all at once.

Does anyone know how to do this please?

Thanks so much for your help.

I want to have another go at Javascript. I have several books on the subject but I find that my eyesight is a major problem. Therefore I want to try an on-line solution, preferably free.

I have Googled, but there are so many that I am almost dizzy with the choices.

Perhaps someone could recommend one. Not too fussy visually. My knowledge is VERY basic.

Frank

Does anyone know how to make URL links that use Javascript still work when
users have Javascript disabled on their browser?

The only reason I'm using JS on a URL is because my link opens a PDF file, and I'm forcing it not to cache so users have the latest version.

I tried the <script><noscript> tags, but I'm not sure if I'm using it
correctly, as my URL completely disappears.

Below is my HTML/Javascript code:

<p class="download">
<script type="text/javascript">document.write("<span
style=\"text-decoration: underline;\"><a href=\"javascript:void(0);\"
onclick=\"window.open(
'http://www.webchild.com.au/mediakit/Direct_Media_Kit_Web.pdf?nocache='+
Math.floor( Math.random()*11 ) );\" >The Child Magazines Media
Kit</a></span> (PDF 1 MB) ");</script>
<noscript><span style="text-decoration: underline;"><a
href="http://www.webchild.com.au/mediakit/Direct_Media_Kit_Web.pdf"
>The Child Magazines Media Kit</a></span> (PDF 1 MB)</noscript>
</p>


Thanks for any help,
Michael

Hi Guys,
I am new at JavaScript and start to do some tutorials.What I am trying to do here is prompting user to input a name and if the name was valid the page(document) will display with all objects like the button.But if user enter a wrong name then the button will be disabled!
I create the following code but it did not work

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>New Web Project</title>
<script language="JavaScript" type="">
function changeColor(){
document.bgColor = "Gray";
}
</script>
</head>
<body>
<script language="JavaScript" type="text/javascript">
var person = "";
person = prompt('What is Your Name:');
if (person == "Foo") {
document.write("<h1 />Welcome " + person);
document.bgColor = "Yellow";
}
else {
document.write("<h1 />Access Denied!!!!");
document.bgColor = "Red";
document.getElementById("gree").disabled = true;
}
</script>

<div>
<p/><input id="gree" type="button" value="Gray " onClick="changeColor();">
</div>
</body>
</html>

as you can see I used the:
document.getElementById("gree").disabled = true;
but it did not work , could you please give an idea how I can solve this problem?
Thanks

Hi,

I have the following code snippet:
test.html
======
<script language="javascript" type="text/javascript">
var testVariable = "test";
</script>
<script language="javascript" type="text/javascript" src="test.js">
</script>

test.js
=====
var testVariable = window.top.testVariable;

In firefox, I'm able to access testvariable defined within test.html in test.js.

But in chrome, test.js couldnot get the window.top.testVariable field defined in test.html.

Can any one please let me know how i can make it work in chrome?. Am i missing something here?.

Hey,
I've got to make the values of some textboxes change the co-ordinates of my sprite on a canvas and havent a clue on how to do it,

Here is my form with the two textboxes and submit button:
<form>
x: <input type="text" name="x" /><br />
y: <input type="text" name:"y" /><br />
<input type="submit" value="Submit"/><br />
</form>

And i need it so that they change the values of these:

//this shows where my sprite will start on the canvas
var block_x;
var block_y;
searched the internet for hours and cant really find anything i understand or works.
any help is much appreciated

I want to insert this js snippet
Code:

function addText(smiley) {
    document.getElementById('message').value += " " + smiley + " ";
    document.getElementById('message').focus();
    return false;
}

to a loaded iframe with name&id chtifrm. I can access it & change embed something in its html via using something like:

Code:

 $(parent.chtifrm.document.body).append('<div id=\"smly\" style=\"cursor:pointer;float:left;top:200px;display:none;position:absolute;\"><\/div>');

....
Code:

parent.chtifrm.document.getElementById('chatbox_option_disco').style.display == 'none'

but how do I insert js in the head of loaded iframe?

Hi Guys I am trying to modify the functionality of my page. I want to be able to activate this piece of code using another javascript function.

This is the code I want to activate:

Code:

<script type="text/javascript"><!--
$('#button-cart').bind('click', function() {
	$.ajax({
		url: 'index.php?route=checkout/cart/update',
		type: 'post',
		data: $('.product-info input[type=\'text\'], .product-info input[type=\'hidden\'], .product-info input[type=\'radio\']:checked, .product-info input[type=\'checkbox\']:checked, .product-info select, .product-info textarea, .date_data input[type=\'text\']'),
		dataType: 'json',
		success: function(json) {
			$('.success, .warning, .attention, information, .error').remove();
			
			if (json['error']) {
				if (json['error']['warning']) {
					$('#notification').html('<div class="warning" style="display: none;">' + json['error']['warning'] + '<img src="catalog/view/theme/default/image/close.png" alt="" class="close" /></div>');
				
					$('.warning').fadeIn('slow');
				}
				
				for (i in json['error']) {
					$('#option-' + i).after('<span class="error">' + json['error'][i] + '</span>');
				}
			}	 
						
			if (json['success']) {
				$('#notification').html('<div class="success" style="display: none;">' + json['success'] + '<img src="catalog/view/theme/default/image/close.png" alt="" class="close" /></div>');
					
				$('.success').fadeIn('slow');
					
				$('#cart_total').html(json['total']);
				
				$('html, body').animate({ scrollTop: 0 }, 'slow'); 
			}	
		}
	});
});
//--></script>

And this is how I want the format of the function to be:

function testsession() {
if there is a session called 'hiredate' {
activate the script above
}
else {
var el = document.getElementById("product_data");
}
}


I just dont know how to write this in javascript

Could you help me if possible please

I got an index.php
Code:

<html>

<form action="bacakomik.php" method='post'>
<select name="kodekomik">
<option value='../komik1/|23'>Judul Komik1</option>
<option value="../komik2/|20">Judul Komik2</option>
<option value="../komik3/|10">Juduk Komik3</option>
<option value="../komik4/|20">Judul Komik4</option>
</select>
<input type="submit" />
</form>
<?php
echo ('<select>');
echo ('<option value= "'.$i.'">'.'Page '.$i.'</option>');
echo ('</select>');
?>
</html>

As you can see, each of the option brings specific value "../komik1/|23"
komik1 is a directory
| is a delimiter
23 is the pages in one chapter and can be considered also as how many images are there on a specific directory

This is my bacakomik.php
Code:

<?php
$dirkomik = $_POST['kodekomik'];
$exploded = explode("|", $dirkomik);
echo ($exploded[0]); //picture directory
echo ("<br>");
echo ($exploded[1]); //total page in the comic
$pagecount = (int)$exploded[1];
//Take last posted value, process it right away
echo ('<FORM name="guideform"> ');
echo ('<select name="guidelinks">');
$i=1;
do  {
echo ('<option value= "'.$i.'">'.'Page '.$i.'</option>');
$i= $i+1;
}while($i <= $pagecount); //Printing option and select
echo ("</select>");
?>
<input type="button" name="go" value="Go!" onClick="document.getElementById('im').src=document.guideform.guidelinks.options[document.guideform.guidelinks.selectedIndex].value+'.png';"> </FORM>
<img src="img0.jpg" id="im">

With the current code on bacakomik.php, I only can change the img src of id "im" in the same directory only. What I want is that the Javascript could "add" the "$exploded[0]" variable so that the picture can be loaded from different directory. Anyone can do this?
I believe that the fix should be somewhere on input tag inside OnClick, or do you know where?

Anyway, I found this on the net
http://p2p.wrox.com/php-faqs/11606-q...avascript.html
Please help me to those who can...