Develop Reference

sending ajax request but not getting right result.Js

i am trying to display the data fetched from database in the loop and between loop i call the function and send ajax request its not working.Actually its displays the only if i used alert command. If i used alert then the browser display the div and then alert if i clicked ok then it displays the second div then again show alert.
Here is the js code
function like(divid,id,session) {
var orgnldiv=document.getElementById(divid);
var ndiv=document.createElement('DIV');
var idd=id+5000;
ndiv.id =idd;
ndiv.className="likeclass";
orgnldiv.appendChild(ndiv);
var dynamicdiv=document.getElementById(idd);
var span=document.createElement('span');
var spanid=idd+5000;
span.id=spanid;
span.className="spanclass";
dynamicdiv.appendChild(span);
var xmllhttp15;
if (window.XMLHttpRequest) {
xmlhttp15=new XMLHttpRequest();
} else {
xmlhttp15=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp15.onreadystatechange = function() {
if (xmlhttp15.readyState==4 && xmlhttp15.status==200) {
document.getElementById(spanid).innerHTML=xmlhttp15.responseText;
}
}
xmlhttp15.open("GET","spancount.php?postid="+id+"&userid="+session);
xmlhttp15.send();
// alert(spanid);
}
please suggest me what can be the reason of this problem my code is working well only if i use alert

The reason why your code works when you use alert is because whenever the alert function is called. The program flow is paused. In other words, your loop wont continue to make another Ajax call until you dismiss the alert.As a result, the request gets handled properly and the response data appears in the span div. that is why I had mentioned to make your calls synchronous instead.
So to answer the question you asked in the comment, Yes at times too many Ajax calls can be a problem. Let's say that the loops runs more than 15-20 times, that means 15-20 simultaneous requests. Now, think about the number of times the same request is being handled by the php script? Definitely a problem here!
Even with Jquery Ajax, the chances of the loop completing successfully is also 50-50 actually because it all boils down to the amount of requests being made , the bandwidth being used and how the request is being processed at the server.
One possible way to fix this problem is : Rather than constantly requesting small peices of data again and again from the server in the loop, Make one Ajax call and get the entire data as json. Then, parse the json and append data to the spans by using the particular span id to extract the relevant data from the json object.
You might have to do a little bit of tweaking in both the above javascript and spancount.php . But it will definitely Save you A LOT of bandwidth. You gotta consider the fact that more than one person could be using your site!!
Hope that cleared up things, all the best with your project :D

Using GET method to get href attribute of an object

What i'm trying to do is what i thought would be quite easy, but it doesnt seem to be working. I want to get the href of an object and all the function is returning is undefined.
This is the page that i'm requesting and what i'm trying to retrieve is the href held in the element of the first seller (who's ClassName is ui-link-inherit)
var buy = $.get(
"http://m.roblox.com/items/24826737/privatesales/",
function (data){
alert($(data).find(".ui-link-inherit:eq(0)").attr('href'));
}
);
I thought it was a permissions issue at first but it still wont work even if you run that on the page.

Did you tried to just alert the data you get?
If there is no .ui-link-inherit ofc it wont work and since .ui-link-inherit seems to be a class of jqueryUI which adds the classes after the page is loaded via javascript, you wont get this class via GET
//EDIT: I dont get all this "you cant access the data cause ajax is asynchronus". He is using the get-fukction completely right. He can access data since data IS the returned stuff from the server. Did I miss something that you all get this that way?

You cannot return a value from that function, it is executed asynchronously. Instead just wait for the AJAX to finish and then do something with the result
// don't do this
// var buy = $.get(... etc...);
// the variable buy will never have any value
// do this instead
function getHREF(){
$.get(
"http://m.roblox.com/items/24826737/privatesales/",
function (data){
var buy = $(data).find(".ui-link-inherit:eq(0)").attr('href');
doSomething(buy);
}
);
)};
function doSomething(buy) {
// in here do whatever you want with the ajax data
}
$(document).ready(function () {
getHREF();
});

The site does not allow Cross-site HTTP requests. Read here: HTTP access control

jquery - scope getting lost in variable

I am developing application which will get some dynamic content which is irrelevant to my question. and the question is
var pat;
$.post('venki/path.jsp', { nam:nam } , function(data) {
pat=data;
alert(pat); //it will displayed the received code form path.jsp
});
alert(pat);// it will not keep the data received from path.jsp
Now I need to not lose the scope.
For example:
var pat=0;
$.post(
pat = 1
);
alert(pat);
It should alert 1 and not o
In java, i should use static. In jquery, how to declare static variables.
Got an answer:
Its simple and very useful and no need to worry about synchronous. the answer is tricky...

it is because post request is not completed when you are alerting pat value. To ensure that value is modified, alert it inside post success function:
var pat;
$.post('venki/path.jsp', { nam:nam } , function(data) {
pat=data;
alert(pat); //modified value
});

If i'm not mistaken, the $.post is async so the pat is not losing it's scope but executed before the pat=data executed
To make it synchronous call look at this question: how to make a jquery "$.post" request synchronous

How to obtain jquery post return values?

I want to retrieve the height and width of an image on a server by using an ajax post call to a php file which returns a double pipe delimited string 'width||height'
My javascript is correctly alerting that requested string from the php file so the info is now in my script but i cannot seem to access it outside the $.post function.
This works:
var getImagesize = function(sFilename)
{
$.post("getImagesize.php", { filename: sFilename, time: "2pm" },
function(data){
alert(data.split('||'));
});
}
But retrieving is a different matter:
// this line calls the function in a loop through images:
var aOrgdimensions = getImagesize($(this, x).attr('src')) ;
alert(aOrgdimension);
// the called function now looks like this:
var getImagesize = function(sFilename)
{
var aImagedims = new Array();
$.post("getImagesize.php", { filename: sFilename },
function(data){
aImagedims = data.split('||');
});
return "here it is" + aImagedims ;
}
Anyone able to tell me what i'm doing wrong?

You are misunderstanding the way that an AJAX call works. The first "A" in AJAX stands for asynchronous, which means that a request is made independent of the code thread you are running. That is the reason that callbacks are so big when it comes to AJAX, as you don't know when something is done until it is done. Your code, in the meantime, happily continues on.
In your code, you are trying to assign a variable, aOrgdimensions a value that you will not know until the request is done. There are two solutions to this:
Modify your logic to reconcile the concept of callbacks and perform your actions once the request is done with.
Less preferably, make your request synchronous. This means the code and page will "hang" at the point of the request and only proceed once it is over. This is done by adding async: false to the jQuery options.

Thanx for the Asynchronous explaination. I did not realize that, but at least now i know why my vars aren't available.
Edit: Figured it out. Used the callback function as suggested, and all is well. :D

Modifying the DOM based on an AJAX result with jQuery

I'm unsure of the best practice for modifying the DOM based on an ajax response. I'll try to let the code do the talking because it's hard to explain.
// page has multiple checkboxes
$("input[type='checkbox']").live('click', function {
var cb = $(this); // for the sake of discussion i need this variable to be in scope
$("form").ajaxSubmit({ dataType: "script" });
}
The server sends a response back, and the js gets eval'd and that means "cb" is out of scope.
What I've done so far is create a couple of helper functions:
var target = undefined;
function setTarget(val) {
target = val;
}
function getTarget() {
return target;
}
And that turns the first snippet of code into this:
// page has multiple checkboxes
$("input[type='checkbox']").live('click', function {
setTarget($(this));
$("form").ajaxSubmit({ dataType: "script" });
}
Then on the server's response I call getTarget where I need to. This seems hackish... Any suggestions?

It's unclear what you're actually trying to do, but I feel like you want to be looking at the success parameter for that AJAX call. The success callback function should execute in parent scope and do what you're looking for.
See 'success' on this page in the jQuery docs.

So what you are trying to do is get the form to submit the content via ajax whenever the user checks/unchecks a checkbox? And because there are several checkboxes, you need to find out which one triggered the submit, so you can change its value to whatever is stored on the server?
If you submit the entire form everytime, why don't you reply with all the checkboxes values, and then change each and every one of them? If not, get the server to reply with the id and the value of the checkbox, then use jquery to find the checkbox with that ID and then change it's value.

How about:
jQuery(function($) {
// give it scope here so that the callback can modify it
var cb,
cbs = $('input[type="checkbox"]');
cbs.live('click', function {
// taking away var uses the most recent scope
cb = $(this);
// disable checkboxes until response comes back so other ones can't be made
cbs.attr('disabled', 'true'); // 'true' (html5) or 'disabled' (xhtml)
// unless you are using 'script' for something else, it's best to use
// a callback instead
$('form').ajaxSubmit({
success : function(response) {
// now you can modify cb here
cb.remove(); // or whatever you want
// and re-enable the checkboxes
cbs.removeAttr('disabled');
}
});
}
});