Develop Reference

ajax to an html site is getting 200 but the response is empty

An example:
this is the site I'm trying to get the HTML:
https://stackoverflow.com/questions/2294493/how-to-get-the-position-of-a-character-in-python
and the AJAX call
$.ajax({
url: href,
type: "get", //send it through get method
success: function(response) {
var htmlElem = $($.parseHTML(response));
console.log({response})
},
error: function(xhr) {
//Do Something to handle error
}
})
the response is empty ("") all the time, can someone know why? and how to fix it?
EDIT:
Loading cross-domain endpoint with jQuery AJAX
this is not fixinig the issue

Jquery: Probably a syntax Issue in ajax() method - Value not getting sent

I'm able to dump value of the variable message in console .
But im not able to send it off in POST Request.
AJAX call:
chat.throwmsg = function(message) {
if ($.trim(message).length != 0) {
console.log(message);
$.ajax({
url: 'ajax/chat.php',
type: 'post',
data: { method: 'throw', message: message} ,
success: function(data) {
chat.fetchmsgs();
$('textarea#entry').val('');
}
});
}
}
This maybe due to wrong syntax, but I've tried both single and double quotes, and combination as well .

With a wild assumption, you are not having any error messages in developer console and chat.php has a post handler forthese parameters
Since your data is JSON, please change the code as this way and have a try..
var temp={ method: 'throw', message: message};
var param=JSON.stringify(temp);
$.ajax({
url: 'ajax/chat.php',
type: 'post',
data: param ,
dataType: "json",
success: function(data) {
chat.fetchmsgs();
$('textarea#entry').val('');
}
});

after reviewing the code I could not find any issues that restrict the data to be sent along with ajax request,if you are having any syntax errors you should have been warned prior the request initialization, however I recommend you to check the request header in the network tab of browser console and see your sending data along with the request if it's there you probably need to check the code of getting the post data in your server-side implementations

"Uncaught SyntaxError: Unexpected token <" after successful HTTP Request

I am trying to do AJAX using jQuery with an ODATA REST service provided by an SAP backend system.
$.ajax({
type: 'GET',
url: 'http://sapxx.sapms/sap/opu/odata/.../',
async: true,
dataType: 'jsonp',
username: 'username',
password: 'password',
crossDomain: true,
success: function() {
alert('Done.');
},
error: function() {
alert('Error.');
},
});
The request returns status 200 and I get a response from the server which is called something like "?callback=jQuery3100687..." and contains xml code. All this is visible in the Chrome debugger. But after the successful HTTP Request I get the aforementioned error
Uncaught SyntaxError: Unexpected token <
I suspect the error is due to the "dataType" parameter which is set to "jsonp" in the request. Is there any way to work around this error? The server can only respond using XML format. The request only works when the dataType is set to "jsonp", I guess because it enables CORS. After sending the request, I get the "Error" alert despite the 200 status.

You say you get an xml response from the server. Your ajax request is set up for jsonp, though:
dataType: 'jsonp',
Try this instead:
dataType: 'xml',
success: function(xml) {
//remainder of the code
}
If you set the dataType to jsonp, jQuery will try to parse the response as JSON. This results in errors, because the response ins't JSON.

Ajax request failing?

I am trying to retrieve json data from an api.
It keeps failing, but when I look in the Net tab of Firebug I can see that the GET request executed and returned the correct data. Am I doing something wrong or does anyone have tips on how to debug this?
Edit: Have changed to dataType json and error status code is 0
Thanks
$.ajax({
url: 'http://localhost:55894/api/Test/All',
data: {
format: 'json'
},
error: function () {
alert('Error');
},
dataType: 'jsonp',
success: function (data) {
alert('Ok');
},
type: 'GET'
});

From the info you provided the reason it is failing is because you dont have a cross domain access policy setup. Because you are using different ports to host the website and the API you are running into this issue. You can either setup a crossdomain.xml with the proper security settings or you can move both the API and the webserver to the same port.
Have a look at this for more info: http://en.wikipedia.org/wiki/Same-origin_policy

u can try this way:
$.ajax({
type: 'GET',
url: 'url api here',
beforeSend: function() {
},
success: function(data) {
},
error: function(xhr) { // if error occured
},
complete: function() {
},
dataType: 'json'
});

JSON and JSONP are different. If you are using JSONP, the server side must be prepared to support it. Doesn't look like you are using JSONP.
So just change dataType to 'json', as you are "trying to retrieve json data".

Catch / Handle 502 Bad Gateway Error

I have to update a large collection so I am calling in a loop an web api. I use jQuery.ajax()
Something like this:
$.ajax({
type: 'GET',
url: 'http://www.somesite.com/API/API.php',
jsonpCallback: 'API_SC4',
contentType: "application/json",
dataType: 'jsonp',
data:'action=update&page='+collection[currentIndex].name+'&callback=API_SC4',
async:false,
success: function(data) {
//use data for update of collection[currentIndex]
UpdateNext(currentIndex+1);
},
error: function(e) {
//interpret error
UpdateNext(currentIndex+1);
}
});
The problem is the collection is quite large and sometimes I get a 502 Bad Gateway error and the ajax error handler is not called.
I even tried $( document ).ajaxError() but i'm doing a cross-domain jsonp call , and it seems .ajaxError() does not get called in that situation.
Is there any way to handle that error? Something at window level?
I can see the error in the Chrome development console , and I was thinking there might be a way.
Thanks

Yes, there is: statusCode. See the jQuery documentation on AJAX for details.
Simple example:
$.ajax({
statusCode: {
502: function () {
alert('Fail!');
}
}
});