I'm currently engaged on a dissertation which is
investigating AJAX technologies and I was
wondering if anyone had any references that might
shed light on the subject?
I will of course carry out a literature review but
in the mean-time has anyone any (preferably print
based) sources of data on AJAX?
Is it true that Javascript has no clone() method, to pass an object by copy of value instead of reference?
If I have an object and want to make an array out of all of its instance variables, I can loop through it and pass its values to a new array, and the class instances will be passed by copy and not by reference?
Example 9.3: References Themselves Are Passed by Value
// This is another version of the add_to_totals() function. It doesn't
// work, through, because instead of changing the array itself, it
tries to
// change the reference to the array.
function add_to_totals2(totals, x)
{
newtotals = new Array(3);
newtotals[0] = totals[0] + x;
newtotals[1] = totals[1] + x;
newtotals[2] = totals[2] + x;
totals = newtotals; // this line has no effect outside of the
function.
}
Note that this rule applies not only to pass-by-reference, but also copy-by-reference. You can modify an object through a copy of a reference, but changing the copied reference itself does not affect the object nor the original reference to the object. This is a more intuitive and less confusing case, so we don't illustrate it with an example.
I am a bit new to JavaScript objects, I have the following object:
LinkTest=function() {
// init
}
LinkTest.prototype.eventHandler=function(){
// the call below fails, as 'this' refers to the link that
// generated the event, and not the instance of LinkTest object
this.doSomething();
}
LinkTest.prototype.register=function(link){
link.onclick = this.eventHandler;
}
LinkTest.prototype.doSomething=function() {
// do something!
}
So basically when you register a link, the onclick event handler gets a reference to LinkTest's eventHandler function. Now when the user clicks on the link, the 'this' refers to the link... how do I reference the instance of LinkTest object from within the eventHandler function?
I discover a strange bug in Konqueror 3.1.1.
I design a javascript application which acts in one file called
example.html. At the beggining of this js i write:
if (document.images)
{
folderopen= new Image(16,16);
folderopen.src="http://www.sergioamo.8m.com/buttons/folder_open.png";
folderclose= new Image(16,16);
folderclose.src="http://www.sergioamo.8m.com/buttons/folder_close.png";
}
functions....
....
...
..
and my javascript works perfect.
If i write:
if (document.images)
{
folderopen= new Image(16,16);
folderopen.src="./buttons/folder_open.png";
folderclose= new Image(16,16);
folderclose.src="./buttons/folder_close.png";
}
functions...
....
...
..
my javascript does not work properly. Does anyone knows if is imposible
to use relative references with konqueror 3.1.1 or which is the problem?
Apparently, there is a page with multiple frames, where one of the
frames is a "hidden" frame, and is there just to contain one or more
"fields" that are referenced from other frames.
Supposedly, if a user "sits" somewhere in this set of pages for
several minutes and then tries to do something, the page redisplays,
but an inter-frame reference (to the "hidden" frame) fails with some
sort of a "No permission" error. If the user navigates through the
site with no real delay, they don't see this problem. This is the
situation I need to understand.
I'm assuming that the "No permission" error occurs when a frame that
was obtained from domain "foo" tries to reference a frame that was
obtained from domain "bar" (I'm not sure of the correct terms in the
context of JavaScript). Under normal operation, all of the frame
contents are obtained from the same domain (I believe).
My theory is (without much information yet) that there must be a
proxy/cache server in between. When the user navigates through the
site with no delays, all of the frames are obtained from the same
server (either the cache server or the target server, I don't know
which). However, when the user "sits" for a while, I'm guessing that
the cache server hits a content timeout, and a redisplay of the page
causes one frame to be obtained from the target server, and one from
the cache server.
Does this seem like a reasonable explanation for what we might be
seeing? What are useful strategies for fixing a problem like this?
I am trying to make a function that checks/unchecks a checkbox when a specific <td> is clicked. I need to use this same function for several checkboxes in the page so I want to just pass it the name of the checkbox I want to affect as a variable and use it in the object reference lines. BUT, this doesn't work. I can pass the variable to the function as I've used alert(variable) to test this. But it doesn't work when I put it in a line like this "document.forms[0].variable.checked=true;". Code:
View 4 Replies View Relatedis there a way to shorten something like:document.scoresheet["HomeTotalHCaps"].valueto a simple short name like var1.value ?
View 8 Replies View RelatedTHE QUESTION: How do I get a reference to my Object when processing an
event handler bound to an html element ?
CONTEXT:
Sorry if it is a bit long.
I am developing a JS calendar tool. One of the requirements is that the
calendar will need to display a varying number of months (1..3)
depending on the calling page. Imagine 1, 2 or 3 calendar pages side by
side as required.
I have built a grid object that will contain one month's dates with the
day names at the top. The calendar object inherits the grid object as an
array of "calendar pages" - one grid per month and the calendar provides
the content for each grid. I will use the grid object for another
completely different object later and so I want to use good OOP
encapsulation. The grid is a table generated on the fly and is "dumb" as
far as what it is used for.
I have attached an onlick event to each cell of the grid. Using OOP
priciples I want the calling program (the calendar object in this case)
to provide a function to handle the click and the grid object will
provide to the calendar the row and column of that cell as well as the
grid number (so the calendar can work out which date was clicked since
it knows what the data means and the grid doesnt). Code:
I'm working on a project that I want the user to be able to change the color theme of the site. For some reason if I go over about 20 themes or css references it breaks the site. Any idea why this is? if so, how can I get it to accept say 50 themes?
View 2 Replies View RelatedI 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've spent several days trying to work this out. Maybe I'm just
searching for the wrong keywords/phrases.
I have some code that looks like:
[-- snippet starts --]
Console = new Object();
Console.init = function() {
this.STDIN = document.getElementById('console0_stdin');
this.STDOUT = document.getElementById('console0_stdout');
// set styles on the element references, eg:
this.STDIN.style.width = �`%'
this.STDOUT.style.width = �`%'
}
Console.focus = function() {
this.STDIN.focus();
}
Console.writeln = function(buffer) {
this.STDOUT.value += "
" + buffer;
}
[-- snippet ends --]
I'm not sure why, but the Console.focus() and Console.writeln() methods
just don't seem to be able to use the DOM references stored in
Console.STDIN and Console.STDOUT. Everything's fine in the
constructor, but other methods can't seem to use them.
My site's working perfectly in the other browsers, and when I delete line 28 (see below) it works in IE but not exactly how I want. Is there a way to retain two jquery references on a single page in IE?
This is the head section of my code:
Is it possible to test whether two objects are equal using the data they contain inside and not comparing their pointers with ==?
Well actually of course there is but...
Is there a way to do it without actually looping through the object, instead maybe something that came with JS? (something like a .equals() method from other programming languages.)
I am confused about the true difference between the two below examples.
first example:
// Demonstrating a problem with closures and loops
var myArray = [“Apple”, “Car”, “Tree”, “Castle”];
var closureArray = new Array();
[code]....
Here we iterate through the length of myArray, assigning the current index of myArray to theItem variable. We declare closureArray 4 times as an anonymous function. The anonymous function in turn declares the predefined write() function, which is passed parameters. Since write() is in closureArray() a closure is created??? During each iteration, theItem is reassigned its value. The four closures reference this value. Since they reference this same value and since this value is reassigned ultimately to the value of the fourth index position, tHe time we execute closureArray later on, all four closures output the same string. This is because all four closures are within the same scope "the same environment" and therefore are referencing the same local variable, which has changed.
I have a couple of problems with this example:
1) I thought a closure is a function that is returned - the inner function is not returned above.
2) theItem is not even a local variable of the parent function (closureArray) - I thought in order for a closure to work, the inner function only accesses the local variables of the outer function, but in this case the local variable is defined OUTSIDE of the parent function.
3) the "the four closures are sharing the same environment." The thing is even in the second example, they are sharing the same environment.
Second example:
// A correct use of closures within loops
var myArray = [“Apple”, “Car”, “Tree”, “Castle”];
var closureArray = new Array();
[code]....
Here we iterate over the length of myArray (4 times), assigning the index of myArray to theItem variable. We also return a function reference to the closureArray during each iteration (closureArray[i]), where i is index number so we assign 4 functon references. So when we iterate through myArray, we immediatelly call the writeItem() fucntion passing an argument of theItem at its current value. This returns a child anonymous function and when that child function is called, it will execute a block that calls the predefined write() method. We assign that returned anonymous function to the variable closureArray. Hence, closureArray holds a reference to that anonymous function. So closureArray during each iteration holds a reference to the anonymous function and we later call closureArray, which in turn calls the anonymous function, therefore calling the predefined write() function to output the local variable of the parent function. This outputs each distinct index of myArray.
This is because since we created the closure, when we call writeItem, passing theItem argument, since theItem is a local variable of the parent function of the closure, it is never destroyed when we later call closureArray (the reference to the child anonymous function)? Yet weren't we using a closure in the first example as well? So whey wasn't those variables preserved?
I don't think it has anything to do with assigning a returned anonymous function to closureArray. Even though an anonymous function creates a new memory position in the javascript engine, therefore not overwriting the other function references we create during the iteration, it's still referring to a local variable declared outside the reference. So if it's about the closure retaining value of parent's local variable even after exiting the parent function allowing for the current indexes to be preserved, then why did the closure in the first example fail to retain each index?
I'm creating an AJAX page that is built using a PHP Class, ie the php looks a bit like this: PHP Code:
$wp_page->addjs('../var/savepolicies.js')
$wp_parser->page = "userpolicywindow.php";
$wp_parser->addlink("Home","../index.php","");
$wp_parser->addlink("Logout","javascript:logout();","");
$wp_parser->getpageid("501");
[Code]...
within this page that has been created, there is an AJAX tree folder which calls another page to be loaded into a DIV by AJAX again. Code:
[Code]...
I don't know why it doesn't work because the page has been loaded with the JS file, but as soon as the link is added afterwards it doesn't work. I take it this is because it doesn't know where to find the JS, but how can I overcome this?
jquery provides ajaxStart() and ajaxStop() events. Those two events do not seem to be triggered if the ajax requests are made by Microsoft Ajax tool Kit (from ASP.Net code). Is there any way to bridge those two event models? If not currently possible, is there any future initiative or plan out there to make this happen?
View 2 Replies View Relatedi was using $.ajax method to get my ajax page on my main page,which is working great.But now if i have links in that ajax page then i can't open them in that same div,the links are opening in new window,but i want to open in same part,i tried google it and then found, i have to use iframe instead of div.how to do with only use jquery and div.
View 3 Replies View Relatedi have a series of <select> fields. The first one, via ajax(), generates a 2nd one, based on the first ones' data with the .change() method. there is then a 3rd <select> - who's data will depend on choice of the second one although step 1 works, and i can generate the 2nd one, i still can't generate the 3rd one.
when i test the script on its own, both the 2nd and 3rd <select> fields are fine - but not via the ajax, which leads me to believe that the .change() from the 2nd one, isnt triggering the ajax call - its not being picked up (even the 'hello' alert isnt working).
[Code]...
I am using jquery for getting ajax responses from server side functions.
I am in a situation where I need to make two ajax calls one after another and the second one is dependent on the response of the first one.
I have tried to use a code which is similar to this one?
$.ajax({
type: 'GET',
url: 'myURL',
success: function(data)
[Code]....
Is it possible to get two have two ajax calls , one dependent on the other?
Am calling Webservice in one ajax post, In the success funtion am calling another another method in same webservice through another ajax post method. First ajax post is getting called and returning the string from the webservice method but the inner ajax call is not getting called. I have placed the code here.
[Code]...
Am trying to set up a very simple AJAX script for my website. The
javascript i have in an external file which reads as below.
This works perfectly in firefox but IE doesn't display anything at all.
No error messages, just a blank IE window. If you look at the IE source
this html is all there it just won't show it! Code:
I was playing a little bit with a lot of ajax frameworks. I have even
wrote one small by myself. But one thing still drives me crazy: Whenever
I'm doing an ajax call I need to specify handler to handle data coming
from a server script. That means that almost for every action I need two
functions.
Since I'm still new to all of this I'd like to ask how can i achieve
something like this:
function function_name(el) {
var i_need_this = get_what_i_need(el.id);
return _i_need_this;
}
where get_what_i_need function is returning some information using ajax
from a server.
I want to update part of a XML output (generated by Perl CGI). I'm using XSL to transform the XML.
Can I use this approach?
I need to resort the contents of a table, that gives me the results
from a query, when someone clicks on one of the names of that table.
Is there any books i can buy from local shops or any websites that can help you learn the basics up to advanced ajax?
View 8 Replies View RelatedI've noticed a strange behavior with Ajax in internet explorer. In my page I've four links, that call four different pages by using XMLHttpMethod. By entering for the first time in the page and selecting the various links, all work correctly (the 4 pages are called and displayed into the page), but if I click again on a link previously clicked, trying to repeat the call, the responseText won't to appear!
View 2 Replies View RelatedI'm new in javascript and ajax and I need a IDE to write and debug my codes and I want it to be something like phpdesigner or dreamwawer that have snipper and suggest me when I write some of the code.
View 2 Replies View Related