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?
View 8 Replieswhat'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?
View 14 Replies View RelatedI'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]...
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.
View 5 Replies View RelatedWhat 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?
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
I pulled out an old javascript object I created a while back a few days ago and I've been developing in Firefox ever since. Then I decided to test how it worked in other browsers and.....it works in none of them! Not chrome, not IE(7/8), not opera, and not safari.
It's built like this:
Code:
function myCalendar() {
//constructor function
}
myDiv.prototype.newMethod = function() {
[Code].....
It's really as simple as that....what's on the go? Do any JS experts out there know anything about this?
What 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...
I've previously written an image carousel with lightbox and to be honest forgot about it for quite a long time. I've just been tasked with making a few modifications (I wrote this code about 6 months ago)
Now, the problem I have is that I now need to call the internal method from the ligthbox plugin.
I've tried setting a reference to this like this but it just won't play ball. I can see that the ajax feed gets called but unfortunately I can't then access it.
[Code]...
I have a javascript function that needs to access methods of a java
object(localTag). In my JSP I'm trying to include hidden fields for
the Strings returned from the getter method calls of the object like
so:
<html:hidden name="FrmCustomerHolding" property='<%=
"localTag.getTagName()" %>' />
<html:hidden name="FrmCustomerHolding" property='<%=
"localTag.getTagValue()" %>' />
If I can do something like this, what is the correct syntax and how do
I access this property in my javascript? When I have a hidden field
that is just a String, I access it in the javascript like
"document.getElementById("theString").value" and it works fine, but I
can't seem to find how to access the String value of a method call.
I have a text field
<input type="text" id="f">
I transorm it to autocomplete widget$('#f').autocomplete()How to access widget's methods and properties by id of the field?I need to access initialized widget to call some of its methods, modify properties etc.
I have an object on the document element that allows for other components to register with it, i have a custom event something along$(document).bind("register",function(thechild)..So in the child object when they are created i call$(document).trigger("register",this);And indeed i get the DOM object. However i'm looking for the plug in object, i want to be able to call methods on the passed childobject and access it's Config.Does that make sense? How can i write a plug in that is applied to various objects that also registers itself with an 'overseer' object on the document element in such a way that i can allow that overseer object to call methods on any registered child objects?
View 2 Replies View RelatedHow 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.
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
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?
I am trying to figure out what the constructors for the Image object are.
I have figured out that in IE and Mozilla, the Image object, and the
HTMLImageElement are the same, from a property perspective at least, but
what is the constructor for the Image object?
I know that I can call the following constructors, but are there others?
Image()
Image(int x, int y)
I could not find any actual spec for this.
So our companies cms is quite javascript heavy. In an attempt to make it leaner I'm attempted to put all of our javascripts into as few files as possible, and compressed. For our form validation I've using the qforms library which consists of many files. Putting them into 1 file with all the other scripts and I receive the error "Field is not a constructor" Here's the piece of code creating the error.
Code: this[field] = new Field(o, field, this._name);
[Code]...
I would be getting this error?
Why this backward way is so often used for constructors:
myConstructor = function() { /*empty placeholder*/ }
// and then:
myConstructor.prototype.methodOne = function() {...}
myConstructor.prototype.methodTwo = function() {...}
instead of right away:
function myConstructor() {
this.methodOne = function() {...}
this.methodTwo = function() {...}
}
Is it just a tradition or is it a workaround of some problem I'm not
aware of?
Can you pass an array reference to a constructor? I don't know if it's because the syntax is screwy or it's impossible, but the following doesn't work.
// row constructor with array called fields
function RowObject(fields)
{
this.fields=new Array();
this.fields=fields;
}
row=new RowObject(fields);
alert(row.fields[0])
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)?
View 4 Replies View RelatedI 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?
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.
View 3 Replies View RelatedTrying to create an object in Javascript (for Appcelerator/Titanium).The "object" is defined like this:
function server () {
this.cacheimages = 0;
this.login = "";
[code]....
In the same file, in another function when I run this line: var server = new server(); I get the error Result of expression 'server' is not a constructor.I have tried it with and without the "return" line, neither work.
I'm looking for the constructor parameter list for DOM Objects. I was able to find a constructor for Option but none of the others.
Code:
myForm = new Form(params);
myForm.elements.push = new Select(params);
myForm.elements[0].options.push = new Option('Select this!','1');
This is a lot cleaner than
Code:
myForm = document.createElement('form');
myForm.setAttribute('name','theForm');
....
Where I can find a list of these constructor parameters?
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
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(){}