The code is very complex so i have simplified below in order to confirm if the behavior i am experiencing is normal or due so some other error i have made in the code.
I have two separate ajax requests that each have their own unique call back. I do not care which one completes first and one has no dependency on the other
function ajax(url, cbS){
$.ajax({
url: url,
contentType: 'application/json',
dataType: 'json',
success: function(data){
cbS(data)
},
});
}
function callbackSuccess1(data){
$('#div1').html(data)
}
function callbackSuccess2(data){
$('#div2').html(data)
}
//request#1
ajax(myapiurl+'&peram1=100', callbackSuccess1);
//request#2
ajax(myapiurl+'&peram2=200', callbackSuccess2);
The problem: Sometimes callbackSuccess1 gets the data intended for request#2 and vice versa.
It seems that which ever request completes first fires callbackSuccess1 and the second to complete fires callbackSuccess2.
I need the callback to be bound to it's specific request so that regardless of the order in which they complete each request fires it's proper callback.
OTHER INFO: My backed is django-tastypie, at this point i am thinking that tastypie is somehow messing up the response. That is the only logical conclusion, given that the javascript seems to be immutable.
The proof that this is actually occurring is that when i inspect the responce on request#1 the data objects are clearly intended for request#2...
CONCLUSION:
Thanks for confirming that 'each invocation of your ajax() function will create it's own closure'. This was what i thought was going wrong. I found the problem in my API. I was doing some funky stuff and it looks like I had a variable that was not getting trashed in time causing the API to return the wrong data if the first request took longer than the second.
The only issue I see with the code you have included is that the function argument is cbS, but you are calling cbs(data) - note the different capitalization.
Other than that, each invocation of your ajax() function will create it's own closure and have it's own arguments and those arguments will be preserved separately for the internal success callback. This is an important capability in javascript and it works. It does not get the arguments of one call confused with the callback of another as long as you are not using any global variables or state that might change during the execution of the asynchronous ajax call.
You could probably use jsonp and specify callback query parameter in URL for $.ajax
callback would be the name of javascript function which is to be invoked whenever the response is returned from server.
For more details please refer jquery doc : http://api.jquery.com/jQuery.ajax/
For theory : http://en.wikipedia.org/wiki/JSONP
This is mainly used for cross-site ajax calls.
Related
I am using jquery for ajax calls
All the calls are called immmediately on page load and we are getting the responses at almost the same time.
the issue is, the 3 calls are fired and I am getting the data, but the callback function is fired for the first call only.
the other two callbacks are not called, the callback is defined as a separate function,
If I just write an alert instead of calling the callback method, all the 3 alert message are coming
So the issue is when we write the callback method, do any one have any idea of the strange behaviour?
We tried to reorder the calls, the behaviour is similar, which ever is called first, its callback will be called, for the rest, it will not be called
var url = "/test1";
ajaxCall(url, testMethod1, false);
var url = "test2";
ajaxCall(url, testMethod2, false);
var url = "test3";
ajaxCall(url, testMethod3, false);
testMethod1:function(data){
console.log("first"+data);
},
testMethod2:function(data){
console.log("second"+data);
},
testMethod3:function(data){
console.log("thrid"+data);
}
ajaxCall is defined as jquery ajax, the issue is only the testMethod1 is called, the rest 2 are not called
Regards
Hari
Well the thing that immediately caught my eye is that the URL for test1 has a forward slash preceding test1. This means that you are using a valid link in only test1. The alerts will trigger because you are probably not trying to access the data returned (which would still work even though the ajax request fails), where as you are trying to access the data in the coded call back functions you have provided, which will obviously throw a NullPointerException or whatever the equivalent as the ajax call fails due to an incorrect URL. Therefore data never gets set and the code doesn't work.
Whenever I try to find answer of this question everyone refers to ajax start/stop etc.
I am using XUI JS's XHR function for cross domain calling, now I want exactly like this
callMyXHRfunction();
callNextFunctionWhenAboveFunctionResponded();
i.e. I should move forward until unless my xhr function responds (either success or failure)
Update
Use Case:
There is a function called getAllData(), this function get all my current data submitted to server. I need to call this function often to get the latest data and move ahead. While loggin I call this function to get latest data and after every 10 mins I need to call this to get data refreshed.
So if I call each my function on success function then my code may confuse other developer and if I write like above he/she will easily know what is going on in first line and in 2nd line.
Hope now everyone understand my situation very well.
See third example on the website you are referencing:
x$( selector ).xhr( url, fn );
Second argument can be a callback, callback being the keyword you were probably looking for to begin with.
Alternatively, use a synchronous call by supplying async: false as an option.
x$("body").xhr("http://the-url",{ async: false });
Control flow will pause until the request returned and only then continue with your next function. See http://jsfiddle.net/ZQ9uw/ for reference.
You need to make the .xhr call in a way that specifies a callback function and pass in your "next" function as the callback.
So you'd write it like this:
callMyXHRFunction(nextFunctionToCall); // no parens after nextFunctionToCall!
function callMyXHRFunction(callback) {
$("something").xhr(url, {
error: callback, // so that nextFunctionToCall is called on error
callback: callback, // so that nextFunctionToCall is called on success
async: true
// add more options here
});
}
i set up a webservice thats cross domain and needs to be contacted via json with padding
on a simple jquery codeline like this, i am successfull getting back json data.
$.getJSON("http://server/series/hist?jsonp=?", function(data){
console.log(data);
});
the webservice, will wrap the result in a function, whenever "jsonp" exists within in the url.
for those cases i used a default function name like:
myfunction({"a":1})
jquery helps me out here, and trys to call the function, that isnt existing ("myfunction()"). what i am trying to achieve instead is a simple call of the callback function (see above), to handle the data locally.
can you point me in the right direction?
thank you
I'm not quite sure what your problem actually is, but:
Interpretation 1
Assuming that by "locally" you mean "without using a callback":
That is impossible. JSON-P cannot work synchronously as it depends on the addition of a <script> element (which won't be processed until the current function has finished executing).
Interpretation 2
Assuming that by that isnt existing ("myfunction()") you mean "Your webservice always uses the function name myfunction:
Fix the webservice. jsonp=? means "Randomly generate a function name and pass it as the jsonp parameter.
The webservice must use that parameter to determine the function name used, and not use a fixed value such as myfunction.
Interpretation 3
You don't want to use JSON-P as the input, but to call your anonymous function directly.
You can't. It isn't stored anywhere you can access it. You have to rewrite your code so it isn't passed directly to getJSON:
function myFunction(data){
console.log(data);
}
$.getJSON("http://server/series/hist?jsonp=?", myfunction);
myfunction({"a":1})
I am attempting to do some dynamic loading that includes javascript, css, and html files.
I would like to do it like this:
$.when($.ajax(htmlPath), $.get(cssPath), $.ajax({
url: javascriptPath,
dataType: "text"
}))
.done(function(response){
// i want to pass the data for each of these to the respective functions
appendHtml(what goes here??);
appendCss(what goes here??);
executeJs(what goes here??);
})
.fail(function(){
console.log("failed");
});
So I'm confused on how I separate out the response callbacks. Currently, the response object you see in my .done function is ONLY the HTML file which I called. This function is making the correct ajax calls, and the correct files are all being responded by the server, but how do I access them once ALL the calls are complete? Need this so I won't be applying css/js to HTML which is not there yet, etc. Also, what I do is have the javascript file returned as a string and then i eval() it within the executeJs function. My understanding is that this is an okay use of eval because its the file being returned by our own server so I don't see how it could be tampered with. Is this assumption correct?
Furthermore, in my appendCss function, I'm just adding it to a "style" element in the head. Is there a big issue with this? I am using all this to make a "widget/app based" functionality where I have a js,css,and html for each "app", and I just want to query the server for them when they are needed and the app is loading.
If your downloaded data is being retrieved from the same server as your original web page, then yes, generally, you would have the same level of trust in that code as you do in the code that's already running in the browser.
The problem with eval() in a context like this isn't necessarily that you don't trust the code coming back from your own server; it's that someone might be able to alter the running javascript so that the javascriptPath variable points somewhere you didn't expect it to.
As far as your actual question goes, your done callback will actually be passed three parameters, because your when call included three promises.
Because of the way that you defined your callback (as function(response)), you are only seeing the first one -- the return value from the HTML call. The other two parameters are being ignored.
Each of the three parameters that you are being passed will be an array of three elements: [wasSuccessful, statusText, jqxhr]. To do something useful with them, you could structure your callback something like this:
$.when($.ajax(htmlPath), $.get(cssPath), $.ajax({
url: javascriptPath,
dataType: "text"
}))
.done(function(htmlResponse, cssResponse, jsResponse){
if (htmlResponse[0]) {
appendHtml(htmlResponse[2].responseText);
}
if (cssResponse[0]) {
appendCss(cssResponse[2].responseText);
}
if (jsResponse[0]) {
executeJs(jsResponse[2].responseText);
}
})
(Assuming that you have the appropriate appendHtml, appendCss, and executeJs functions written already)
There are some good examples on this page: http://api.jquery.com/jQuery.when/
And this page has the documentation on the jqxhr object (the third element in each of the arrays that are passed to your done function): http://api.jquery.com/jQuery.ajax/#jqXHR
To access to all the responses just pass three arguments to the done() callback. Try this:
$.when($.ajax(htmlPath), $.get(cssPath), $.ajax({
url: javascriptPath,
dataType: "text"
}))
.done(function(responseHTML, responseCSS, responseJS){
console.log(responseHTML[0]);
console.log(responseCSS[0]);
console.log(responseJS[0]);
})
if you try to print arguments object inside done() you can clearly see that all the responses are passed into the callback
Regarding the use of eval, consider using JSONP instead (dataType: 'jsonp'). This way jQuery takes care of executing the code for you. I suppose jQuery also uses eval() under the hood, but then at least you know that it is done in a proper manner. With respect to safety, also see the related question on when eval() is evil if you haven't already.
The jQuery documentation lists the following example of using $.getJSON to request JSONP:
$.getJSON("http://api.flickr.com/services/feeds/photos_public.gne?tags=cat&tagmode=any&format=json&jsoncallback=?",
function(data) {
$.each(data.items, function(i,item) {
$("<img/>").attr("src", item.media.m).appendTo("#images");
if (i == 3) return false;
});
});
Rather than use this method, which generates a dynamic callback function name because of this parameter:
jsoncallback=?
I want to be able to set that in advance to a hardcoded function name, like this:
jsoncallback=test
This works, in the sense that I run the script and the JSONP that I get back has the JSON object wrapped in a call to test().
However, I can't figure out how to set up the callback function. Shouldn't it be as simple as this?
function test(data) {
console.log(data);
}
$.getJSON("http://api.flickr.com/services/feeds/photos_public.gne?tags=cat&tagmode=any&format=json&jsoncallback=test");
When I try that, I get back the JSONP which is wrapped in test(), but the function test() that I've defined is never called. Am I missing something?
Thanks for any help!
As defined in the documentation for you to use the following method
jQuery.getJSON(...)
you need to specify callback=? when making a JSONP call. I usually only uses this for response types of "json". For response types of "jsonp", you want to use:
jQuery.get(...)
and specify the type as "jsonp". See this documentation on the subject. But that is also bound by the fact of having to have a callback=?.
What I think you are looking for is this:
jQuery.getScript(...)
Which should execute whatever method you have defined in your callback.
Ah, the "Related" sidebar section saved me here. After I submitted this question, I found a similar one already asked:
using a named function as the callback for $.getJSON in jQuery to satisfy Facebook request signing demands
Duncan's answer from Oct. 15 solved this for me:
window.fixed_callback = function(data){
alert(data.title);
};
$(function() {
$.getScript("http://api.flickr.com/services/feeds/photos_public.gne?tags=cats&tagmode=any&format=json&jsoncallback=fixed_callback", function(data) {
alert('done'); } );
});
I guess the key is using $.getScript instead of $.getJSON. One can still specify an anonymous callback function in the parameters of the $.getScript method, which will be executed after the callback function named in the request URL parameters ("fixed_callback" in this case). Hope this helps someone down the road.