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?
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?
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?
View 14 Replies View RelatedCan 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 RelatedI 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 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 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'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 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 RelatedI 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(){}
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;
}
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:
I have an assignment where one piece of it needs to have the first name, last name, area code, and phone number when prompted by a function, once that info is had, it then needs to use the constructor function that is there to process the data and lastly use the data to output it with a show function. I have it to work with static information, but cant seem to figure what I am missing or how to make the prompt function information to feed to the constructor, I know when using the static variable it uses "new Function" but that seems to be my problem, I am stuck.
see the code below:
<!DOCTYPE html PUBLIC "-W3CDTD XHTML 1.0 TransitionalEN" "http:www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http:www.w3.org/1999/xhtml">
<head>
[Code]....
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?
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]...
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?
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 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]...
Code:
function BaseController(el) {
var that = this;
this.defaultAction = function() {
[Code]....
What is the proper method here so that el will be defined in the super "class".? I know I saw something on stack overflow a couple of days ago but can not seem to find it again.
admin: Something is up with the code tags, why the system is double posting the code. Does HIGHLIGHT=JS not exists anymore? – That seemed not be working.
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.
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.