Prototype Inheritance
Mar 4, 2007In my research in the javascript language I have encountered problems
with implementing prototype inheritance while preserving private
methods functioning properly. Here is an example: Code:
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Object's Prototype Variable Inheritance
Aug 29, 2006I'm looking to do something like this:
function superDuperObject(range) {
this.startContainer = new superDuperObjectStartContainer(range);
}
function superDuperObjectStartContainer(range) {
this.calculatedContainerNumber = doSomethingAndGetSomethingBack(range);
return range.startContainer
}
function doSomethingAndGetSomethingBack(range) {
return
someCoolInformationThatICalculateInThisFunctionTha tNeedsTheRange;
}
var myObject = new
SuperDuperObject(DOMRangeObjectThatIDefindedEarlie rInCode);
// Show me the startContainer of
"DOMRangeObjectThatIDefindedEarlierInCode"
alert(myObject.startContainer);
// Show me the calculatedContainerNumber that I get from a function
that does stuff with the range passed to it
alert(myObject.startContainer.calculatedContainerN umber);
Inheritance : Access To The SuperClass' Methods Via Prototype
Sep 20, 2005What I am trying to achieve is an 'inherits' method similar to Douglas
Crockford's (http://www.crockford.com/javascript/inheritance.html) but
that can enable access to the superclass' priviledged methods also. Do
you know if this is possible ?
In the following example, I create an ObjectA (variable a), an ObjectB
which inherits ObjectA (variable b) and an ObjectC which inherits
ObjectA (variable c1). The 'toString ()' method of ObjectC refers to
the 'toString ()' method of ObjectA. This is possible because the
'Object.inherits ( superClass )' method adds a reference to the
superClass of an object in the object's prototype.
If I understood things correctly, the prototype is the same for all
objects of class ObjectC. Therefore, I should be able to only add the
reference to the superClass once. That is the purpose of the
'Object.initializedPrototypes' array : it keeps track of the objects
for which a reference to the superClass has been added to the
prototype.
However, when I create another instance of ObjectC (variable c2), its
prototype doesn't contain any reference to the superClass.
A workaround for this problem consists in adding a reference to the
superClass for each instance of the inferiting object (either by
bypassing the check to Object.initializedPrototypes or by adding the
reference to a priviledged member such as 'this.superClass' instead of
'this.prototype.superClass'). However, in terms of memory usage or of
"programming elegance", this seams to defeat the whole purpose of using
prototypes.
Here is the code, if any of you have got ideas...
Inheritance Question
Mar 3, 2005Suppose I have:
Code:
function A() { ... }
function B() { ... }
What's the difference between:
Code:
B.prototype = A
and
Code:
B.prototype = new A
?
Inheritance Issues
Aug 17, 2006Let's consider this example:
function Polygon(iSides) {
this.sides = iSides;
}
Polygon.prototype.getArea = function () {
return 0;
};
function Triangle(iBase, iHeight) {
Polygon.call(this, 3);
this.base = iBase;
this.height = iHeight;
}
Triangle.prototype = new Polygon();
Triangle.prototype.getArea = function () {
return 0.5 * this.base * this.height;
};
Here are my questions:
1/ "Triangle.prototype = new Polygon();" : Doesn't this line overwrite all the properties already defined in the Triangle function?
2/ "Triangle.prototype = new Polygon();" : Won't this same line assign this.sides an empty string (or undefined ??) if one considers that the polygon function has no arguments? Or does writing ...prototype = new SomeClass() only "touch on" the methods?
Difference Between Object.prototype And Function.prototype?
Nov 25, 2011According to ECMAScript, the root of the prototype chain is Object.Prototype. Each object has an internal property [[Prototype]] that could be another object or NULL.... However, it also says that every function has the Function prototype object: Function.Prototype, it confused me, because a function is an object, for a function object, what is its function prototype and object prototype..For example:
var x = function (n) {return n+1;};
what is the relationships of x, Object.Prototype and Function.Prototype
How Come Object.prototype Inherits From Function.prototype
Dec 14, 2009I am trying to get to the bottom of javascript object, prototypes etc. I have a fairly good grasp of it, but I get confused the closer I get to the base object.prototype. FIrst of all, I was under the impression that all objects descend directly from Object. But some objects (like Array) seem to inherit properties and methods from the function.prototype. So does this mean that the chain is like this:
object -- function -- array Second, I noticed (on the mozilla javascript reference site that object.prototype inherits properties and methods from function.prototype and vice versa!? How can this be? I must be missing something important about understanding the chain?
Classes Inheritance Problem
Jul 23, 2005I've discovered the following problem while building an APP:
/* Code Start **************************/
// Definition
function cClass_prototype_prototype()
{
this.array = new Array;
this.className = "cClass_prototype_prototype";
}
function cClass_prototype()
{
this.className = "cClass_prototype";
}
cClass_prototype.prototype = new cClass_prototype_prototype;
function cClass1()
{
this.className = "cClass1";
}
function cClass2()
{
this.className = "cClass2";
}
cClass1.prototype = new cClass_prototype;
cClass2.prototype = new cClass_prototype;
oClass1 = new cClass1();
oClass2 = new cClass2();
// Testing
alert(oClass1.array)
alert(oClass2.array)
oClass1.array.push(1);
alert(oClass1.array)
alert(oClass2.array)
/* Code End ****************************/
If you will execute this code you will see that pushing an value into
the first class instance array property cause changing value of the
second class instance array property.
Is it possible to have array values not connected to each other?
I would like to avoid defining "array" property in cClass1 and cClass2
(in this case it would work the proper way) and have them defined only
in third-level parent class cClass_prototype_prototype.
Noodle With Prototypal Inheritance?
Jul 30, 2010please bear with my noobishness, but i've been trying for many hours to understand what is going on behind this code:
[Code]...
actually construct an instance of Employee if the reference to its constructor has been replaced by an instance of Person that only contains name and age properties? how is Ken ever initialized by Employee constructor?
JQuery :: Classes - Objects And Inheritance ?
May 28, 2010Basically i have a good experience and knowledge with prototype.js library and also at the same time i am willing to get deeper into jquery.
I very much use oops concept now a days in almost every problem i solve using javascript, and was doing with prototype's feature to create classes and objects. Since i am now looking to get deeper into jquery, i was looking to find similar feature in jquery as well. I suppose jquery must be having a feature to create classes and do inheritance programming, but i couldn't find the way. My question to the forum is, Is there any option/feature in jquery which helps us to create classes and objects of our own probably with the support of inheritance?
Benefits Of Prototypal Inheritance Over Classical?
Dec 29, 2010What are the benefits of prototypal inheritance over classical inheritance?
View 1 Replies View RelatedFailure Of Inheritance From A Style Statement?
Oct 20, 2009The first div in this example has the position property stated in the div itself.
The second has it stated in a separate style statement, and it doesn't get inherited, though another property from the same style statement DOES.
Firebug makes no complaints.
Is there a better way to refer to the jquery library files, so that you don't have to fix my pointers to my local library?
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
[Code]....
Resolved Inheritance And Nested Objects (non-DOM Related)?
Nov 17, 2009I 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. $(function()
[Code]...
With And Prototype
Aug 24, 2005I can use "with" like this:
function MyObject(message)
{
this.message = message;
}
function _MyObject_speak()
{
alert(this.message);
}
with (MyObject)
{
prototype.speak = _MyObject_speak;
}
I was wondering why I can't use "with" like this:
with (MyObject.prototype)
{
speak = _MyObject_speak;
}
Cracking Prototype.js
Jul 23, 2005One of the complaints about prototype.js (google for it if you're not
familiar with it) is that it's poorly documented. I have this inkling
that the key to understanding prototype.js is in the bind function.
The problem with Javascript is that the "this" operator is poorly
overloaded and it is often hard to understand in the context of
object-oriented javascript
So, let's start with the definition:
Function.prototype.bind = function(object) {
var method = this;
return function() {
method.apply(object, arguments);
}
}
As I read this, it states that all functions (which are themselves
objects) will, in the future, have an associated method called "bind".
The function() function, so to speak, simply instantiates a Function
object with the parameter list and then evals the statement, sticking
the resulting execution-tree in the current code frame.
The "this" there refers to the function object associated with the call
to bind(), right? But the word "arguments" there refers to the
arguments passed to the function object *generated by* the call to
bind().
In every example within prototype.js, bind() is called either in a
constructor or within a method contexted to a javascript object, and is
always called with "this" as its argument, e.g.:
this.options.onComplete = this.updateContent.bind(this);
As I read the code it seems to be stating that the "this" object
referred to within bind()'d functions are being coerced into always
referring to the current instantiated object.
But isn't this always the case anyway? Is this a rather confusing
attempt to ensure "this" purity whereby the call
method.apply(object, arguments)
is forced to always have the reference to the containing object present?
I think I've got it. Bind() generates uniq functions that contain live
references to the objects to which they belong, such that the function
object can then be passed to setTimeout() or onMouseOver(), handlers
that accept functions but not objects.
Object.prototype
Mar 15, 2006Lets say we run: window.alert = function() { };
Is there anyway to 'restore' the original alert() method or is it gone
forever?
I know you can do window.alert = Window.prototype.alert, but lets say
you also set Window.prototype.alert = function() { } or lets say we're
in Opera, which doesnt have a Window "class".
Prototype.js BindAsEventListener Without 'this'
Jun 5, 2006I would like to set up an event observer outside of an object, so I
can't use this.bindAsEventListener. How can I pass the correct object
reference?
I tried something like this, and various other variations, but no luck.
This works when I set it up from inside the object, using "this.",
Event.observe(targetId,'click',targetId.select.bin dAsEventListener(this),false);
Object As A Prototype.
Jan 11, 2007I wanted to add an object as a prototype to separate my methods more
nicely, however, I ran into a couple of problems. Apart from the
obvious "scope" issues I found that any instances of my class shared
the objects methods and properties.
I realise (now) that this is actually how prototypes work, they share
functions and objects rather than create new instances of them for
every "class", but is there any way around it? (or shouldn't I be doing
things like this at all?) Code:
Having More Than One Object Without Using Prototype
Jan 23, 2007I am working on my own pop up calendar, mainly because the one I am currently using crashes the Safari browser at times.
So, I want to verify that what I am doing will work, in that I want to be able to have multiple calendars open at the same time, each independent of the other.
So, I start it off with:
var Calendar = {
dateSelected: null,
topPos:null,
leftPos:null,
somefunction:function(e) {
...
}
};
If I create more than one calendar object, will they have their own variables, in that the dateSelected, topPos and leftPos will be unique to that instance?
Or, is there a better way to do this, that is cross-platform.....
JQuery Or Prototype ?
May 16, 2007I want ask you if, for a web portal/application, is better prototype or Jquery? I don't want to innesc some type of flame, but after the announce that drupal use JQuery and that the new Wordpress
2.2 use Jquery I ask myself if my choice of use prototype.js is the bettere choice.
Updating A Div With Prototype
May 17, 2011I have <div id ="changeable"> with some html in it. I have a link that calls the function to replace the info in the div. The problem is that the "creative_development.inc" file is added to the top of the div and does not replace the content. How do I replace the content, and not just add content?
View 1 Replies View RelatedThis.prototype.addEvent
Nov 20, 2007I'm trying to make an addEvent function that will automatically attach itself to the object using a class.
My question is how can I add the function so when I write obj.addEvent("click",myfunction); it will add the event?
Here's my current function:
this.prototype.addEvent = function(type,fn)
{
if(window.attachEvent)
this.attachEvent("on"+type,fn);
else if(window.addEventListener)
this.addEventListener(type,fn,false);
}
IE And Prototype Problem
Dec 13, 2007I need help to workaround the following problem:
First, about the environment:
- The web pages automatically generated.
- Pages can be inserted to each other
- When a subpage to be inserted is being generated, it does not know will it be inserted or not.
- That because each subpage uses the <script src=...> tags to load the script it needs.
- in the external script files I'm trying to protect it from repeated execution checking (if(){}) the value of a variable which is created after in the script.
Everything worked fine until I tried to use the .prototype to declare the method of my objects.
In the Internet Explorer, I got "Object does not support this property or method", on the access to a prototype function, because the prototype of my object was deleted by itself after the second load of the external script. Code:
GetElementsByAttribute() For Prototype
Apr 9, 2006This function will return an array of the elements in a page that contain a certain attribute, you can also give it a value that the attribute has to match, a tag name that the element has to match and a parent element.
I know there are other functions for doing this, but this one is written for use with the prototype (http://prototype.conio.net/) JavaScript library, in fact its really just a modified version of the getElementsByClassName() function that’s part of prototype.
document.getElementsByAttribute = function(attribute, value, tagName, parentElement) {
var children = ($(parentElement) || document.body).getElementsByTagName((tagName || '*'));
return $A(children).inject([], function(elements, child) {
var attributeValue = child.getAttribute(attribute);
if(attributeValue != null) {
if(!value || attributeValue == value) {
elements.push(child);
}
}
return elements;
});
}
Usage is pretty simple, this will return all elements with a width attribute:
XML With Prototype And Geko ..?
Nov 13, 2005I try to get a xml-response with prototype. for e.g. i have the following code:
<html>
<head>
<title>Test Ajax</title>
<script src="prototype-1.3.1.js" type="text/javascript"></script>
<script type="text/javascript">
//<![CDATA[
var getXML = function()
{
var myAjax = new Ajax.Request(
"bsp.xml",
{
method:'GET',
onComplete:showXML
}
);
}
var showXML = function(r)
{
var names = [];
var root = r.responseXML.getElementsByTagName('personal').item(0);
// root
for (var i = 0; i < root.childNodes.length; i++)
{
var node = root.childNodes.item(i); // mitarbeiter
names.push(node.childNodes.item(1).firstChild.data);
}
$('xml').innerHTML = names.join("<br />");
}
//]]>
</script>
</head>
<body>
<p>
<a href="#" onclick="getXML();return false;">TEST</a>
</p>
<div id="xml">
</div>
</body>
</html>
xml-Data:
<?xml version="1.0" ?>
<personal>
<mitarbeiter>
<vorname>John</vorname>
<name>Brown</name>
</mitarbeiter>
<mitarbeiter>
<vorname>Matt</vorname>
<name>Blue</name>
</mitarbeiter>
</personal>
This works fine in IE but in Geko-Browser i got nothing back, because this browsers build the DOM with linebreaks and whitespace. Do you have any ideas what is wrong in my code and how to get propper DOM?
Prototype + Grep
May 16, 2006Having read through Sergio Pereira's Prototype documentation I came across the grep command within Enumerable object.
This is something that looks very interesting. Such as being able to quickly select only the elements you want using a regular expression.
But for the life in me I can seem to get it to work.
Anyone a bit more up to speed with Prototype care to have a look?
var elementList = Form.getElements("just-a-form");
nodes = $A(elementList);
var localElements = nodes.grep( /image/, function(node){
return node.id
});