When a custom object is created in javascript, then methods need to be defined for this object. Still every object has toString() method available to them, even if it is not defined. How is this method available to all the objects ? Is it inherited from some root object ?
Is sort() method available to all the objects ? What are the other methiods available to all objects ? Where can I get list of available methods ?
Can assign a new function to a built-in object in Firefox:
But IE and Opera don't have a MouseEvent or HTMLElement that can be set up in the same way. Can you do this in IE or Opera, or just Firefox, and maybe Webkit?
I created a method for displaying an object's properties:
As long as renderfunction = false, the object is fine coming out of this function.
However, if I change renderfunction to true, all my properties become undefined. Why isn't this working as I expect it to?
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.
When you use addEventListener (or addEvent in IE) to call an object
method, does it call it with the correct this parameter?
The ECMAScript reference has a lot to say about the caller using
Function.prototype.call or Function.prototype.apply and passing the
correct this pointer for the context, but how does addEventListener
determine the correct this pointer. Or does it just punt and pass the
global context, thus making it impossible to refer to the object this
in an object method used as an event listener?
I have more of a programme design related question here: I have an object with 2 methods, those two methods are supposed to be called repeatedly one after the other (e.g. by setInterval())
window.setInterval(function() {
obj.method1();
obj.method2();
}, 100);
the problem with this code is that the execution time of those methods may increase depending on the processed data (an array with several hundred elements or more) so it may be, that the execution time of both methods exceeds the given repetition time. I could solve that by placing a call to the next function in each method, but I wonder if that is good design or not (tight coupling)
code for method2() is analogue
Obj.prototype.method1 = function ()
{
/* working code here */
[Code]....
I am a little confused how the memory for objects is allocated in
JavaScript. David Flanagan, in "javascript: The Definitive Guide,"
states that each property of a class takes up memory space when
instantiated. So space is created for aMethod three times in this
example: Code:
Let's say I have a Javascript object that looks like this:
{
events: {
"comments:added": this.add,
"comments:removed": this.remove,
"comments:fetched": this.addAll
}
}
I'd like to add this method to it, either manually, using $.extends() or _.extends():
[Code]...
Do many programmers remember most of the object properties and methods or do they use IDE or references to find those specific objects. I'm starting to learn Javascript and seeing all the different type of objects available can be depressing. :(
View 2 Replies View Relatedi have something like this:
Code:
var o = {
f1:function(a) {
[code]....
Code JavaScript:
function dropdown() {
}; dropdown.prototype = {
sele: $('.select'),
city: [],
scope: [],
type: [],
init: function(json) {
if(json.location.length) {
for(var i=0; i<json.location.length; i++) {
this.city[i] = json.location[i].city; .....
this.scope[i] = json.location[i].scope;
}}.....
getUrl: function() {
return location.pathname+location.search;
},
setUrl: function(paramType, param) {
return this.QueryString(paramType) ? this.setQueryString(paramType, param) : this.getUrl()+"&"+paramType+"="+param;
}};
Well, I've been working with JS for three years and have a great experience here. But! I still have no really acceptable answer to the following
question:
What is the principle difference between declaring methods/properties
in the constructor function body and via prototypes.
Are there any real GURUs? Let's discuss the issue.
I'm attempting to understand the use of privileged methods when used with Object.create. I put together a quick demo (code below) that shows what happens when I use Object.create to create a new object based on one that has a privileged method. The outcome is not pleasant, as changing the value in the first object also changes it in the second. Unless I am reading Crockford's articles incorrectly, this makes Object.create almost useless for anything but objects that have only public members.
I've seen many JavaScript programmers use closures extensively to create private members, and that still holds to be a good programming practice. However I still can't find an elegant way to create inheritance in combination with closures in JavaScript, given downfalls such as the one I mentioned above.With all of that said I still think Crockford has a nice way of programming, creating factory functions that produce objects, staying away from the prototype property and making the language look more functional.
Here's the code to demonstrate what I'm referring to. Firebug needs to be enabled to view the console.debug output, otherwise convert them to alerts.
if (typeof Object.create !== 'function') {
Object.create = function (o) {
function F() {}
[code]....
What are the different methods of selecting some of the values in the json object below:
what different selecting methods can you use to get the date, or the views?
I have some confusion about the scripts below:
1) is getRule a local variable or global variable, as it has no var keyword, yet it is an inner function of Validation? So without var, I think global, but being an inner function, I think local. So I'm not sure which.
2) In this line of code: var rule = $.Validation.getRule(types[type]), getRule returns rules, which is just a local variable in Validation. I always see that you return functions, but how does returning a local variable that's just an object literal and not a function be able to return true or false? Now the value of rules is an object literal, and this object returns true or false. So we are basically allowed to use return keyword with local variables that are object literals and not functions?
3) In this line, is foo(age) being called, or is it just being assigned to bar OR is it being called and THEN assigned to bar: var bar = foo(age);
4) Now for the most confusing: age is obviously an object reference as opposed to a literal in the example. Does that make a difference in regards to closures?
Note that I read a number of books, including JavaScript Programmer Reference and Object Oriented JavaScript and jQuery cookbook, which compare primitives vs reference types and how primitive types store directly in memory whereas reference tpyes reference memory, so if one reference changes, they all change where primitive remains ingrained. But when assigning a function as a reference like this, how does that affect the object "age" when passed into bar?
Code:
(function($) {
/*Validation Singleton*/
var Validation = function() {
var rules = {
email : {
check: function(value) {
if(value)
return testPattern(value,".+@.+..+");
return true;
}, .....
$.Validation = new Validation();
})(jQuery);
Code:
function foo(x) {
var tmp = 3;
return function (y) {
alert(x + y + tmp);
x.memb = x.memb ? x.memb + 1 : 1;
alert(x.memb);
}}
var age = new Number(2);
var bar = foo(age); // bar is now a closure referencing age.
bar(10);
I have an object on the document element that allows for other components to register with it, i have a custom event something along$(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 RelatedI am looking for a way to put all CSS values on my selected elements back to its default. I was wondering if anyone has maybe done this before and if not has any idea's to get me started.
The idea is that when I use for example:
The elements within .setDefault will return to its default font/color/height/width etc... so basically all posible values.
Can Java classes/objects be used from within the javascript code on the
HTML page? I.e., can I call a Java method from the javascript function?
I am wondering if it is possible to get the response from a method
within a given page, and that function alone? Traditionally, I have
been getting the response from the Page_Load method of the targeted
page, but now I want the response from a particular method on the
target page:
Public Sub SomeCallback(ByVal sender As Object, ByVal e As EventArgs)
'RETURN XML FOR CALLBACK
End Sub
About when to use setter methods. For example, I have this code
Should this be used like this:
I think a better question is when to use the .each loop? Since, the first line of code I have works fine.
So I have this homework assignment where I need to get my application from switches to using methods to give me the same result. I usually am good in this class, but right now I am completely lost. Here is a piece of the code using switches:
/* Get Type of Math problem from the user */
input = JOptionPane.showInputDialog(null,"Enter the type of Math Problem"
+ "you would like to solve:
"
+ "Addition = 1
"
+ "Subtraction = 2
"
+ "Multiplication = 3
"
+ "Division = 4
"
+ "Enter the number of your choice: "); .....
I need to get this same result by using methods. I can use these method signatures:
public static int readProblemType(){}
public static int getAddProblem(int randomValue1 int randomValue2){}
public static int getSubProblem(int randomValue1 int randomValue2){}
public static int getMultProblem(int randomValue1 int randomValue2){}
public static int getDivProblem(int randomValue1 int randomValue2){}
public static int readAnswer(){}
Looking at what I need to do, how would I use public static int readProblemType(){} method to read the problem type? Or where should I start?
Programming assignment: Write a program for analyzing El Paso weather. This program must allow the user to enter dates followed by temperatures at these dates. Assume that we are only tracing one year, so the overall number of such dates does not exceed 366. Your must then output the following information:
*the average temperature;
*the list of all the days when the temperature was below freezing (i.e., below 32);
*the hottest temperature, and the list of all the days when the temperature was the hottest.
Main difference: In the previous assignment, following our advise, you stored the dates in one array (array of strings), and temperatures in another array (array of numbers).
For this new assignment, define a class Record whose objects contain two fields:
*a field date that contains the date, and
*a field temperature that contains the temperature.
Instead of using two arrays, use a single array of records (i.e., of objects of type Record).
The problem I'm having, is that I do not know how to read from two files and store the information into one array. (For example: with this assignemnt, I need to have one array with 366 fields, and in each field there needs to be a date and temperature.)
How are methods masquerading as properties? Does this make methods more flexible as objects or plain functions?
View 6 Replies View RelatedI 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?
Creating methods that can be used by all elements?
View 1 Replies View RelatedI just wanted to know if there was any way to use script to display a
list of methods linked to a particular object? The object I have in
mind is getBrowser(), and I can't seem to find any documentation online
with regards to it's methods.
Also, as I am learning, it would be nice to be able to know what
methods are available for a particular object/function, without
necessarily having to spend a while looking up an object's method when
it's documented in a lot of different places, but only vaguely.