Develop Reference

Put ajax response attribute in to a variable for Google Books cover image

I am trying to put a url from an ajax response into a variable in jquery.
I have written the following code:
var thumb = $.ajax({
dataType: 'json',
url: 'https://www.googleapis.com/books/v1/volumes?q=isbn:' + isbn,
success: function(response){
return $(response).volumeInfo.imageLinks.thumbnail;
}}).responseText;
It was my understanding from looking at other answers that I must add .responseText at the end, or the code will continue without waiting for the ajax response.
However, thumb variable remains undefined.
I tried implementing the following solution with relevant changes (As I am passing only one ISBN at a time, there shouldn't be an array. The response should contain only one imageLinks.thumbnail url), but I cannot seem to catch the response correctly.
I looked into other answers, especially this one, but I am still not clear about how to reach the ajax response.

$.ajax is asynchronous, meaning the code will execute completely and the success callback will be fired at a later time.
var thumb is evaluated immediately. Do some reading on "callbacks" and "promises" to get more familiar with this topic.
A solution to your issue is:
function setThumbnail(thumbnail){
// this will evaluate later, when the ajax returns success
console.log('thumbnail gotten!');
var thumb = thumbnail; // do something with in in this function
}
$.ajax({
dataType: 'json',
url: 'https://www.googleapis.com/books/v1/volumes?q=isbn:' + isbn,
success: function(response){
setThumbnail($(response).volumeInfo.imageLinks.thumbnail);
}
});
// This line will evaluate immediately and carry on
console.log('ajax executed');
I threw in some logs for you to help you understand the order of execution here.
I would also note that $(response) looks odd to me, without testing it I think it should probably be just response.volumeInfo....
console.log(response) in the success callback to make sure you understand what data you are getting back.

AJAX and JSON error handling

I have a form which submits data via AJAX to an external server.
The data which gets sent is then validated and if correct the user can then advance onto the next step of the form.
If the data is not valid, then the server returns an error which is outputted as a JSON object.
I can see the JSON object in FIDDLER.
My aim is to grab that JSON data and output it on the page and notify the user.
Ideally, i would do this as part of an error handler on the AJAX request(found below).
Is this achievable?
PS:
Unfortunately, I can't set up a demo because the link that the data is posted to is only available on my network.
It is also worth pointing out that the error that the back-end script outputs is actually stored in the link that the data is posted to.
AJAX REQUEST:
var setUpVrmData = function() {
$("#getvrmdata").click(function () {
var p_vrm = $('#p_vrm').val();
$.ajax({
dataType: "JSON",
type: "POST",
url: "http://217.35.33.226:8888/l4_site/public/api/v1/BC8F9D383321AACD64C4BD638897A/vdata",
data: {
vrm: p_vrm,
},
success: function(data) {
//Empty the dropdown box first.
$("#p_model").empty();
appendString = "<option value='none'>-- Select your model --</option>";
$.each(data['vehiclemodel'], function (k, v) {
// += concatenate the string
appendString += "<option value='" + k + "'>" + v + "</option>";
});
$("#p_model, #ent_mileage").show();
$('.js-find-my-car').hide();
$('.js-get-price').show();
$("#p_model").append(appendString);
$("#p_model").prop("disabled", false);
$('#skey').val(data['skey']);
},
error: function() {
console.log("We return error!");
}
});
});

The Error function will return an XHR object that you may be able to parse to get the message you want. I don't know what is serving the data so depending on how that's setup your mileage may vary. I've done this using PHP as well as C# and writing to Console, but in both cases I was able to control the returned data.
I used this article : http://encosia.com/use-jquery-to-catch-and-display-aspnet-ajax-service-errors/ as a starting point.
You'll need to update:
error: function() {
console.log("We return error!");
}
to
error: function(xhr, status, error) {
console.log("We return error!");
}
Set a break point there in Firebug to check if an XHR object is passed, if not you'll need to find a way to get it.. You mention you can see the JSON in fiddler, it should be available to you. If it is, just use the eval posed in the article and you should be okay. If not you'll have to go and figure out how to get it, depending on your platform difficulty will vary.
A few things to note, eval is messy and can get you into trouble. In the cases I've done this, I removed the eval in production.
Also as of jQuery 1.8 success error and complete are deprecated. Use done fail and always if you plan on updating jQuery in the future.
jQuery API reference, for reference.
http://api.jquery.com/jquery.ajax/

JQuery ajaxSubmit response always in lowercase

I am making an ajaxSubmit call to a web service, that will return XML.
When I make a call to the same service using XMLHttpRequest.send, the response is correct.
However if I use:
$(form).ajaxSubmit({
error: function _(response) {
$(iframeEl).remove();
config.error.call(scope, Thunderhead.util.JSON.decode(response));
},
success: function _(response) {
console.log(response);
$(iframeEl).remove();
var result = response;
config.success.call(scope, result);
},
iframe: true
});
This returns the correct XML response, but all tags have been transformed to lowercase.
I've checked the call in the Network tab in the developer console, and the case is correct in there, but when it is returned by the ajaxSubmit, it is lowercase.
Does anyone know what is causing this or how to rectify it?

Are you using Malsups jQuery form plugin
This plugin does a lot of toLowerCase transforms, I've not looked too closely but it does seem to lowercase the tag names of something, so this is probably your culprit.
I'd recommend refactoring to using a simple jQuery.ajax() call instead
$(form).on('submit', function(e) {
var url = $(form).attr('action');
e.preventDefault();
$.ajax( url, {
error: function _(jqXHResponse) {
// your code
},
success: function _(response) {
console.log(response);
// your code
}
});

This might be happening, because js is assuming xml as an answer. There is no difference for most xml-parsers which case is used in xml tag names.
I suggest trying to change response data type.
For example there is such option in jQuery.ajax method: http://api.jquery.com/jquery.ajax/ (named dataType). I would try using "text" dataType if case is really important.

Some further issues arose from this in the end, so just posting my eventual solution in case anyone else has this problem. I'm fairly new to javascript, so this might have been obvious to most, but it might help someone else out.
The success callback can actually take in 3 parameters, the third of which (arg2) is the actual response from the request, without any changes from the Malsups form plugin.
So in the end, the solution was simply to use this third parameter instead of the response parameter.
$(form).ajaxSubmit({
error: function _(response) {
$(iframeEl).remove();
config.error.call(scope, Thunderhead.util.JSON.decode(response));
},
success: function _(response, arg1, arg2) {
console.log(response);
$(iframeEl).remove();
var result = response;
config.success.call(scope, arg2.responseXML);
},
iframe: true
});

Uncaught ReferenceError: set_metadata is not defined

I'm using the Yummly API (https://developer.yummly.com/documentation) and I am trying to parse a JSONP list of courses to use in a drop-down box. The format of the file I am requesting (located at http://api.yummly.com/v1/api/metadata/course?_app_id=[My App ID]&_app_key=[My App Key]) is:
set_metadata('course', [{"id":"course-Main Dishes","type":"course","description":"Main Dishes","searchValue":"course^course-Main Dishes"},....................}])
The request seems to work fine, and I can view the results in the Network tab in Chrome. However, in the console I get the error "Uncaught ReferenceError: set_metadata is not defined" I've done a lot of looking around, and have found people with similar but different errors, but I have not understood the cause or why the fixes for their errors work. I am fairly new to jQuery, so I'm guessing I'm doing something wrong with my request, which is:
var coursesURL = 'http://api.yummly.com/v1/api/metadata/course?_app_id=' + appID + '&_app_key=' + appKey;
var courses = [];
//Query for the list
$.getJSON(coursesURL + '?callback=?', null, function(data) {
console.log(data);
//Go through each result object found
$.each(data.course, function(i, course) {
courses.push(course.description);
});
console.log(courses);
});
Any help is greatly appreciated. I would also really appreciate an explanation of what I am missing, not just the fix. Thank you.

The reasons I'm adding this as an answer and not a comment are because i don't have enough reputation to comment and this is the only thing i can find on the yummly api returning jsonp.
I was able to get past the "uncaught referenceError" problem but now its only returning the word 'allergy', which is in the response, and I'm not getting the rest of the data.
here is my code:
$.ajax({
url:"//api.yummly.com/v1/api/metadata/allergy?_app_id=[APP_ID]&_app_key=[APP_KEY]?callback=",
dataType:"jsonp",
jsonpCallback:"set_metadata",
beforeSend:function(){
console.log("sending");
},
success: function (data){
console.log(data);
},
error: function(data){
console.log("send error and returned:");
console.log(data);
}
});
here is the response:
set_metadata('allergy', [
{"id":"392","shortDescription":"Wheat-Free","longDescription":"Wheat-Free","searchValue":"392^Wheat-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"393","shortDescription":"Gluten-Free","longDescription":"Gluten-Free","searchValue":"393^Gluten-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"394","shortDescription":"Peanut-Free","longDescription":"Peanut-Free","searchValue":"394^Peanut-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"395","shortDescription":"Tree Nut-Free","longDescription":"Tree Nut-Free","searchValue":"395^Tree Nut-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"396","shortDescription":"Dairy-Free","longDescription":"Dairy-Free","searchValue":"396^Dairy-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"397","shortDescription":"Egg-Free","longDescription":"Egg-Free","searchValue":"397^Egg-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"398","shortDescription":"Seafood-Free","longDescription":"Seafood-Free","searchValue":"398^Seafood-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"399","shortDescription":"Sesame-Free","longDescription":"Sesame-Free","searchValue":"399^Sesame-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"400","shortDescription":"Soy-Free","longDescription":"Soy-Free","searchValue":"400^Soy-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]},
{"id":"401","shortDescription":"Sulfite-Free","longDescription":"Sulfite-Free","searchValue":"401^Sulfite-Free","type":"allergy","localesAvailableIn":["en-US","en-GB"]}
]);
the line of code that says:
jsonpCallback:"set_metadata",
in the ajax call gets me past the reference error but im not getting the rest of the data that's in the response.
please help?
Finbar

I figured out the problem.
JSONP is returning not JSON text, but a function to the callback. Thus, I needed a function in my code called "set_metadata" that is used upon success of the json/ajax call.
Specifically, I defined function
function set_metadata(course, data) {
//Do stuff here
};
I tested it and that correctly captures the data I am trying to get.

Problems using jQuery AJAX to parse XML

I'm not a very experience programmer and have been learning HTML/CSS/JS on the fly. I've been trying to parse XML using jQuery AJAX methods with absolutely no luck.
Here is my code in use: http://jsfiddle.net/Kb5qj/1/
And here is my code in plain sight:
$(document).ready(function() {
var divid = "#xmlcontent"
function parseXML(xml) {
$(divid).empty();
$(xml).find("CD").each(function() {
var artist = $(this).find("ARTIST").text();
var title = $(this).find("TITLE").text();
$(divid).append("<li>" + artist + " - " + title + "</li>");
});
}
function printError() {
$(divid).html("An error occurred");
}
$.ajax({
type: "GET",
url: "www.w3schools.com/ajax/cd_catalog.xml",
dataType: "xml",
success: parseXML,
error: printError
});
});
I don't know what the problem could be. I have written and re-written and copy/pasted that $.ajax call many many times, but no matter what I do nothing ever happens. Help me please?

like I mentioned it will fail on jsfiddle as they dnt actually send the get request. here is the api on how to achieve the same: http://doc.jsfiddle.net/use/echo.html
If you try the same on your local system it will fail probably cos you are making a cross domain request and your browser natively blocks such requests. That is where jsonp comes it to play its to retrieve json data over cross domains..
You can hack it a little to do the same for js.. here is a SO post about the same: Is there an existing tool for jsonp like fetching of xml in jquery?

With a little bit of fudging, everything in the parsing seems to work fine. Check out this JSFiddle.
You can't use get requests from JSFiddle, but I mocked up the XML into HTML. You may want to try placing your XML document into the DOM to help suss your issue.