Prototype - Override Constructor For A Object?
Mar 23, 2011
I have a requirement to override the constructor of a javascript class. I have to execute the current constructor code and then call a javascript method. Basically, I need to execute a javascript method whenever an object of that particular class is created in addition to whatever is being done now. I do not want to copy and paste the current constructor code and override the initcomponent method. I am looking for an alternative for that.
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Apr 5, 2011
How would I go about copying all the prototype functions AND the constructor from one object into another object, and then call them?
I know I can use this.example.call(this), but that's not an acceptable solution. I want to deploy this style over dozens, potentially hundreds of objects.
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Nov 19, 2009
I had read from books that the constructor property of object is inherited from its prototype. And the prototype can be changed dynamically. New property can be added to or deleted from object even it was created before the prototype change.
But I got confused on below codes.
But the actual result (both IE and firefox) is
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Apr 30, 2010
what's the point of using x.constructor.prototype? (highlighted in red) why not directly use x.prototype. classname to check whether 'classname' property is in this class?
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Mar 29, 2010
I have a class constructor, and after the constructor a prototype method associated with that class. I'm trying to call that method from within the class constructor, but it causes an error, indicating that the method is not a property of the class.Is it not possible to access prototype methods from within the constructor? If it IS possible, how do I do it?
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Jan 6, 2011
I'm not sure why this: Code: console.log(instance2.getAnotherKey()()); returns Object { a = "a" } when I clearly reassigned the value of the a property. Reassigning the property caused change in this line:
Code:
ref.a = 'abc'; console.log(inst.getZ()); //Object {a="abc"} So why does it work when you call an instance method in the constructor (e.g. this.getZ()) but doesn't work when you call the instance method in prototype?
[Code]...
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Oct 30, 2006
What happens if you do this?
function Person() {}
Person.prototype = 7;
var ted = new Person();
Also what happens if you set Person.prototype to an array or function?
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Nov 25, 2011
According 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
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Dec 14, 2009
I 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?
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Feb 9, 2010
I need to detect the "name" of the constructor of an object. For example, myArray.constructor === Array is true, but I want something where that === 'Array' is true. I've heard of Object.constructor.name, but it's not widely compatible. (preferably without involving regular expressions)?
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Mar 20, 2010
I am trying to understand why I had an error, or why my solution worked. In my HTML I had:
<script language="JavaScript" type="text/javascript" src="Book.js"></script>
<script language="JavaScript" type="text/javascript" src="Book_TEST.js"></script>
Book.js said:
[Code]....
Now, the code worked fine in both script. (i.e., no more error.) So far as I can tell, the only differences between the first and next version of Book.js are the comments and the whitespace. Am I missing something? Can the comments or whitespace somehow effect the logic with which this code has been executing? If I get an error like this again, is there an easier/better way to fix it than to essentially retype the code?
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Jul 9, 2010
How to extend the constructor for the date object of the javasccript so that whenever a call is made to the constructor, I want to perform a particular action? Basically how to define wrappers for default javascript methods or objects like Date() so that I can perform some action and then invoke the original method? So basically if I have something like var a = new Date(); I want it to (say) alert the value of the date everything Date() is called and then execute the default date constructor.
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Jan 1, 2011
I need to create a constructor for a computer object. This object must have three properties: speed, and mem_live mem_dead. Then I need to create a new object using this constructor and then have its properties displayed on the screen.Look at what I'm up to so far:
function Computer(speed, mem_live, mem_dead)
{
this.speed = speed;
[code]....
It always just shows : 4.0ghz, true, false
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Aug 8, 2005
function show() {
var s = '' ;
for (var i = 0; i<arguments.length; s += '
'+arguments[i++]) ;
typeof(window) != 'undefined' ? window.alert(s) : WScript.Echo(s) ;
}
function f(){}
show('delete(f):',delete(f)) ; // false
g = function(){} ;
h = new g() ;
show('h:',h) ; // [object Object]
show('delete(g):',delete(g)) ; // true
show('h.constructor:',h.constructor) ; // function(){}
show('delete(h.constructor):',delete(h.constructor )) ; // true
show('h.constructor:',h.constructor) ; // function(){}
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Dec 3, 2005
is there a delete for a object inside the constructor, while i init it?
i will try something like that:
var obj = function(a)
{
if (!a) delete this;
this.a = a;
}
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Jul 20, 2005
Sorry, bad title. Anyway, is there a way to pass the arguments to an object
instantiated via a constructor using the arguments object and have it
expanded, so to speak, so that it doesn't appear as a single argument? I'm
sorry, this explanation is just atrocious, but I can't think of exactly how
to word it. Maybe an example...
Take for instance Function.apply. It takes 1-2 arguments, the first being
the object to use as the context, and the second being either an array or an
instance of the arguments object which are to be the arguments for the
function. I want to do something similar but I want to also basically use
the new operator so that I get back an object.
Here's a snippet of some of my code, maybe this will help:
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Jan 2, 2011
I'm sure this question has been asked many times before, but I can't seem to get the correct terms to find the answer in Google.I understand basic JavaScript inheritance. However, everything I've read makes the inheritance work something like this:
Code JavaScript:
var ChildClass = new Function();
ChildClass.prototype = new ParentClass();
ChildClass.constructor = ChildClass;
That's fine, but what happens when ParentClass's constructor needs parameters?As an example, look at the following code:
Code JavaScript:
function Furniture(color){
this.color = color;[code)....
How could I "copy" Furniture's constructor into the Chair object? Better yet, how could I copy Furniture's constructor and then add some functionality to it?
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Jun 12, 2011
I have a code set up something like this:
[Code]....
The problem is I keep getting an error along the lines of: TypeError: Result of expression 'house' [[object Object]] is not a constructor. It seemed to work when I wasn't passing the other objects as parameters in the constructor. I just created and assigned them later. As in:
[Code]...
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May 20, 2009
I'd like to make a Degree object that inherits from the Number object and uses the Number constructor but adds a .rad() method that returns the value in radians.
If I do something like:
It generally works but I don't get Number's methods like toString and toPrecision.
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Sep 20, 2010
I have static object and I want remake it to a constructor with property 'length' which would be not enumerable in for loop... This is my object and how I generate it
[Code]...
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Mar 15, 2006
Lets 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".
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Jan 11, 2007
I 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:
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Jan 23, 2007
I 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.....
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May 25, 2006
I've created a new class using prototype.js. After I make the ajax.request all references to this.myClassMethodorVariable are lost. Does the ajax method blow out the object persistance? I'm fairly new to OOP javascript so could be (and probably am) overlooking some detail. Code:
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May 7, 2009
QUESTION ONE: When is use of the jQuery prototype object appropriate, and when is it not?
BACKGROUND:I am still trying very hard to identify the error that is prohibiting me from incorporating a jQuery plug-in into my site in a manner similar to the way that the author of the plug-in has incorporated it into his.Although I have sought consultation with the author, he appears uninterested in working with me.My still fledgling knowledge of jQuery tells me that the author of the plug-in and my implementation of his plug-in are constructed differently.Whereas I use jQuery's prototype property to reference my method and then assign my method anonymously to my HTML document as follows: $().myJQMethod().The author of the plug-in does something very different.I have extracted from the author's plug-in and my implementation of it. Links to the source pages have been included.
CONSTRUCT A (The jQ_Impromptu Plug-In):
(function($) {
$.prompt = function(message, options) {
})(jQuery);[code]...
QUESTION TWO: Although I am able to implement the author's method, it is not performing as it should. When the alert box appears with focus the hosting HTML page is suppose to show through with dimmed opacity.My implementation does not achieve this effect. Firebug has alerted to me to the following breakpoint, but I am poorly unable to interpret it.
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Jul 23, 2005
I find the JavaScript's Object.prototype and getter/setter mechanism
very nice. However, I need some help with extending an object with
getters/setters in the derived class. For example:
A : function () {}
A.prototype =
{
a : null,
get a : function () { return a++; }
};
B : function () {}
B.prototype = new A;
Now, I would like to define a getter/setter in B. How do I do that?
There is no way to use the same syntax as in "A.prototype = ..." above.
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