Using New Keyword With Variable Length Arguments?
Dec 22, 2009
I want to use the new keyword to instantiate an object. The catch is I want to pass in variable length arguments.
Given:
function Foo () {
this.args = Array.prototype.join.call (arguments);
}var args = ["arg0", "arg1", "arg2"];
The following don't work (though I understand why):
new Foo.apply (null, args);
new (Foo.apply (null, args));
(new Foo).apply (null, args);
How to do what I want without modifying Foo's source code?
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Jul 26, 2011
So in the Tutorials:How jQuery Works, I've noticed that you can make a call to .get like this : $.get('myhtmlpage.html', myCallBack);
I've also noticed that in the docs jQuery.get() is described as jQuery.get( url, [data,] [success(data, textStatus, jqXHR),] [dataType] ). My question is, in the above example, the callback function is the second argument, whereas in the docs the second argument is data, and the third is the callback function. How does this work? Also, what does it mean when the arguments are laid out in an array-like fashion with commas in the square brackets? i.e. arg1, [arg2,]...
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May 11, 2011
If you specify arguments when writing a function should you still declare the argument variable inside the function?
example:
Code:
or
Code:
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Aug 29, 2010
How can to obtain length of string variable, for example if I have:
var msg = 'hello world!';
Does it exist a method to count string characters?
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Dec 8, 2006
Given the following code:
var xf2;
function f1()
{
if (document.createElement && document.body && document.body.appendChild) {
xf2 = new f2(arguments[]);
}
}
I am getting a syntax error in the "new" statement following the [].
How do I pass the variable-length arguments list received by f1 on to f2?
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Apr 3, 2007
I am modifying the suckerfish dropdown code to use settimeout to have
a slight pause before the menus disappear to make it more user
friendly. I have hit a snag with the following statement:
li.
{
timerID=setTimeout('this.getElementsByTagName("UL")
[0].style.display = "none"', timecount);
}
If I put take the statement
this.getElementsByTagName("UL")[0].style.display = "none";
out of the settimeout function, it works. (w/o the pause, obviously).
With the settimeout function, I get "this.getElementByTagName is not a
function" error.
I have tried putting this.getElementsByTagName("UL")[0] is a variable
and then using that in the settimeout function, but then each li will
only open the very last menu in the list. (ie all the menu items open
the last sub menu) Code:
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Aug 19, 2009
I've been searching google endlessly and I've come to the conclusion I'm not using the proper search keywords. I'm trying to create something similar to the banner/button combo you can find here:[URL]..
I assume these type of slide show buttons combos use java script and possibly php. If anyone knows the proper name for this type of slide show or can point me to some scripting
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Sep 8, 2006
Is there a way to find which element in an object array the keyword 'this'
is acting upon?
For example:
function doMe(){
var aTags = document.getElementById("list").getElementsByTagName("a");
for (var i=0; i<aTags.length; i++) {
aTags[i].onclick=function() {
this.className = "myClass";
}
}
}
Inside of this function is there a way to determine where in the array this
'this' is and return the integer?
var theID = this.somethingOrOtherThatWouldGiveMeTheNumber;
var elementID = document.getElementById("myDiv"+theID);
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Aug 29, 2011
I was reading thegetting started with jquery. And got confused with use of this in these 2 code segments.
$(document).ready(function() {
$("#orderedlist").find("li").each(function(i) {
$(this).append( " BAM! " + i );
});
});
$(document).ready(function() {
// use this to reset several forms at once
$("#reset").click(function() {
$("form").each(function() {
this.reset();
});
});
When do we need $(this) and this? And what is the difference between them?
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May 28, 2009
Would like to check if there is anyway where i can use javascript to grab the keyword of .doc and .pdf file.
because when i right-click on the files, and click on properties. there will be a tab at the top (Summary for .doc and PDF for .pdf), and upon clickin there will the description, author and keywords. so im just wondering if there is any way to grab the value?
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Feb 12, 2011
I'm trying to get the following function to work:
When called like so:
I could just give each image an ID and not use the 'this' keyword, but I haven't used it much so I'm curious about it. It's sending the image element to the function, so why can't I modify the src attribute with that information?
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Apr 27, 2007
I'm creating a list with buttons that show and hide some of the list elements to create the effect of scrolling. I've built an scrollList object so I can apply this to any list. When you create the object and pass it the id of the <ul> and how many items of the list you want to be displayed. It will add the scroll down and scroll up links and add an Event.observe to them (I'm using the Prototype library).
This code creates the object
var main_news_articles;
main_news_articles = new scrollList('main_news_articles', 5);
main_news_articles.init();
The problem I am having is with the callback functions of the onclick event of the links (scrollUp and scrollDown). The this keyword within these functions is refering to the link and not the object.
To try and solve this I've made the title attribute of the link the same as the variable name of the scrollList object. I can reference the scrollList object like so Code:
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Sep 19, 2009
I've just started learning jquery and have been trying to use this code which I found on this forum.I want to detect some text (addClients) in the url and add an css id to a list item with the class m1 (li class="m1") - so I get (li class="m1" id="expanded"):
This is what I have so far (which is not working)$(function() {
$(document).ready(function() {
var url = location.pathname;
[code].....
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May 30, 2010
I want detect if the column has red or blue, add the class on it, it's like
[Code]...
but I want every column 2 below red column and column 3 below blue also add the same css, how to do it?
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Aug 13, 2010
I am looking to insert a keyword in to a javascript alert box when someone visits my website, so say they came from codingforums, it would say "Welcome, CodingForums.com Visitor". My keyword will be passed from the ad platform I am working with and shows up correctly in the tracking, so I'd imagine it's just a case of having the snippet of code for it to show in the alert, correct? If there is no keyword, I would just like it to say "Welcome Visitor" or something.
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Jun 14, 2010
This following script changes style when mousing over a paragraph:
Code:
<html>
<head>
<script type="text/javascript">
[code]...
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Jan 20, 2006
How do I take <%=Keyword%> in Javascript and break it down to arrays?
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Nov 13, 2010
this.delete = function(obj){
..
Is that it ? I can't have delete ? Or can this be written in some other way, including delete ?
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Nov 13, 2011
My plan is to create a JavaScript class, with some functions and variables, and one of the functions is called when a user clicks on a certain element. However, I need to find out the ID of the element that was clicked (in the example, that of the <p>) for further processing. It looks basically like the following:
[Code]...
The result was very crazy, because console.log(this) gave me the node as result, and console.log($(this)) did the same only as jQuery node, but trying to find out the attribute via jQuery gave undefined as result. I haven't checked if this.id would work (should probably), but I'd prefer to keep the whole script in jQuery, if possible. I suspect it may be an overusage of the 'this' keyword, but if so, what's the proper way to do it?
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May 2, 2007
I have some script like this:
// simplified to remove all the try/catches & stuff
function newXHR() {
request = new XMLHttpRequest();
XMLHttpRequest.prototype.requested = null;
return request;
}
then later:
function doRequest(url, callback) {
var req = newXHR();
req.requested = url;
// et cetera....
}
This works fine in Firefox, however the line 'req.requested = url' causes an error in IE7, (I haven't tested IE6 yet). The error is 'Object doesn't support this property or method'
So, this leads me to believe that either a) XMLHttpRequest.requested is not writable, or, b) XMLHttpRequest.requested was never created in the first place. I think it's the first option because I'm not getting an error in the newXHR() function.
I've been searching for some documentation on this but I can't seem to find anywhere if properties created with the prototype keyword are writeable in IE. Does anyone know what the problem is?
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Feb 24, 2009
So I know all about the caviats of the 'this' keyword when calling object functions from event listeners:
Code:
var foo = {bar: true, zoo: function() { return this.bar; }};
foo.zoo();
> true
a = foo.zoo;
a();
>
And I know that I can get around this by using an anonymous function so that 'this' is preserved in it's original context:
[Code]...
But then someone pointed out this article on memory leaks when using anonymous functions to call object methods because the anonymous function gets access to ALL variables in the enclosing environment and my not be properly disposed of by the garbage collector [URL] So that lead me to think about using a "3rd-person" approach to referencing object properties from within object methods.
[Code]...
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Dec 21, 2010
How can I grab the keyword phrase that someone used to enter the website and then pass that through a form? I would need to know for search engines and Google AdWords as well. Does anyone know how to do this?
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Jun 10, 2009
is it possible to combine the the following functions with each other in an array for example and if so, would someone be kind enough to show me how. the reasons are 1. to see if it is at all possible and 2. to learn so that I can combine further possibilities in the future. the first script compares user keywords from search mashines and the second replaces certain strings/paterns with others.
[Code]...
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Aug 24, 2010
I am confused about what the return keyword is actually returning when returning an object, a primitive, or a function. My confusion is compounded by the fact that I'm not sure if a function is an object or not. According to the book JavaScript Programmer Reference it is: "All functions in JavaScript are first class objects , meaning they can be passed around like any other object reference. In fact, regardless of how they are created, functions are instances of a global object named (aptly) Function."
However, someone else states that a function is not an object. An object is a set of primitives and references. A function is executable code. Functions become objects through the use of the new operator. Yet, in the book I mentioned, it says you don't need the new keyword to execute the function as an object, as it already inherits from the object Function when the function keyword is used:
function functionName([argname1 [, ...[, argnameN]]])
{
statements;
}
So there's one source of contradiction. Now the bigger issue is what is going on when the return keyword is used. Notice the Validation() function returns an object as its last expression. This technique is common, where you return an object which contains functions in form of object notation. I believe this is done so that we create a closure so that when the intepreter exits the Validation() method, since we created a closure by returning an object, which contains the inner functions addRule and getRule, the local variables of Validation() are not destroyed, given that we can reference them through the two inner functions that make use of the local variables of the outer function. So when we use the return keyword on an object literal, and then exit the function, when we call one of the inner functions as we do later:
[Code]....
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Oct 12, 2010
First of all excuse me if I posted this thread in the wrong forum, I really have no clue where to put this but I've had some minor experience with js so I hope it can be solved this way. I check websites and/or keywords in googles Keyword Tool External as a free service for some of my clients. The thing is that more and more clients like this service and it's becoming very time-consuming for me to do this for all of them.
Is there a way to let my clients fill in the keywords or url they like researched in a form on my website, then let those words be researched and return a specified number of results in a pdf or something? My biggest concern is the captcha code. If I can't find a way to partially or fully automate this process, I'll be forced to either charge for or completely give up this service.
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Jul 20, 2005
I embedded a javascript in HTML and tried to open the file using
mozilla 1.4 it gave me the following exception in the script on
clicking the Submit/Next button. IE was able to execute the script
Function defination
function evaluate(form)
Line making the call :
<INPUT onclick="if (validate(this.form)) evaluate(this.form);"
type=button value=Submit/Next name=B1>
Mozilla Javascript console window.
Error: uncaught exception: [Exception... "Not enough arguments
[nsIDOMXPathEvaluator.evaluate]" nsresult: "0x80570001
(NS_ERROR_XPC_NOT_ENOUGH_ARGS)" location: "JS frame :: <unknown
filename> :: onclick :: line 0" data: no]
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