Develop Reference

Jquery Ajax Call Return

I have made a function which is the one below that i pass data to and returns the result as is. I made this way because i will be needing a lot of ajax call and i just made a function that i pass the data to and get the result as is and work with the result.
function FunctionsCall(data){
var ret;
$.ajax({
type:'GET',
url: 'includes/helpers/functions.php',
dataType:"json",
data: data,
success: function(result){
ret = result;
}});
return ret;}
Now i am calling it where i need it:
$('#register-name, #register-surname').keyup(function(e) {
var x = FunctionsCall({query: $(this).val(), funcid: 1});
(x!==1) ? $(this).addClass('input-has-error') : $(this).removeClass('input-has-error'); });
But strange is that i always see x as undefined. Pointing out the ret is filled with either 1 or 0 i don't know why it is not being passed to x.
Can you please help me out? It might be simple but i just experiment when needed with javascript and jquery.
Regards

ret doesn't get set until the success function runs, which is when the ajax finishes. FunctionCall returns straight away however. You'll either need to return the ajax deferred object or put your addClass/removeClass functionality in your success function.
A way to add your addClass/removeClass functionality to your success function would be like this:
function FunctionsCall(data, successFn) {
$.ajax({
type: 'GET',
url: 'includes/helpers/functions.php',
dataType: "json",
data: data,
success: successFn
});
}
$('#register-name, #register-surname').keyup(function(e) {
var element = $(this);
var data = { query: element.val(), funcid: 1 };
var successFn = function(x) {
if (x !== 1) {
element.addClass('input-has-error')
} else {
element.removeClass('input-has-error');
}
}
FunctionsCall(data, successFn);
});

The problem is that the ajax call takes time to execute, whereas your processing of x is immediately after the call to FunctionsCall
Imagine that in order to go to the php file and get the result, the browser has to send a request over the wire, the server needs to process the request and return the value, again over the wire. This process takes an unpredictable amount of time as it relies on network connections and server specs / current load.
The code to call the function and process the result happens immediately after this step and as such won't have the required values when it is run (browsers are much quicker at executing the next step than networks are at processing requests).
The best thing to do is to wrap your processing code up in it's own function, so it isn't immediately called, then call that function with the result once you get it. Like this:
// function defined, won't be called until you say so
var processMe = function(result) {
alert(result);
}
$.ajax({
// ajax params
success: function(result) {
// function called within success - when we know the request is fully
// processed, however long it takes
processMe(result));
}
});
You could also do the processing directly in the success block but the advantage of using a function is it's there to re-use in the future, plus, you also get to give it a nice understandable name, like outputValidatedMessage.

you must send ajax request syncronous
function FunctionsCall(data){
var ret;
$.ajax({
type:'GET',
async: false,
url: 'includes/helpers/functions.php',
dataType:"json",
data: data,
success: function(result){
ret = result;
}
});
return ret;
}

Ajax calls are asynchronous.
This means that while you call $.ajax(), the function continues to run and return x which is undefined, as the ajax response has not been send yet.
function FunctionsCall(data){
var ret;
$.ajax({
type:'GET',
async: false,
url: 'includes/helpers/functions.php',
dataType:"json",
data: data,
success: function(result){
ret = result;
}
});
return ret;
}

The below should work for you
function FunctionsCall(data){
var ret;
$.ajax({
type:'GET',
url: 'includes/helpers/functions.php',
dataType:"json",
data: data,
success: function(result){
(result !==1 ) ? $(this).addClass('input-has-error') : $(this).removeClass('input-has-error'); });
}});
}

maybe is because the ajax function is called asynchronously so the line var x= .... doesn't wait for the asignment and thats why is undefined. for that you should use a promise here is an example http://joseoncode.com/2011/09/26/a-walkthrough-jquery-deferred-and-promise/
http://www.htmlgoodies.com/beyond/javascript/making-promises-with-jquery-deferred.html

check if the following works, may be your GET method is taking time to execute.
var x;
function FunctionsCall(data){
var ret;
$.ajax({
type:'GET',
url: 'includes/helpers/functions.php',
dataType:"json",
data: data,
success: function(result){
ret = result;
x= result;
alert(x)
}});
return ret;}
if the snippet works, you should make you synchronous async: false or make callback function

try this code.
function FunctionsCall(data,callback) {
try {
ajax({
type: 'GET',
url: 'includes/helpers/functions.php',
dataType: "json",
data: data,
success: function (result) {
callback(result);
}
});
} catch(e) {
alert(e.description);
}
}
$('#register-name, #register-surname').keyup(function (e) {
var data = {
uery: $(this).val(),
funcid: 1
};
FunctionsCall(JSON.stringify(data), function (result) {
(result !== 1) ? $(this).addClass('input-has-error') : $(this).removeClass('input-has-error');
});
});

Ajax call with nested ajax calls in for each

I'm experiencing the following problem.
I have the following nested / foreach loops ajax call structure:
var children = [];
$.fn.ajaxHelper.loadAjax({
url: someUrlReturningJsonOfChildren,
cache: true,
callback: function(options) {
var json = options.json;
$.each(json, function (i) {
// get the details of this child
$.fn.ajaxHelper.loadAjax({
url: urlForDetailsUsingId,
cache: true,
callback: function(options) {
var json = options.json;
children[i] = json;
}
});
}
}
});
// want to do something with (newly filled) children here
As you can imagine, I'm running into the trouble that the ajax calls are asynchronous (duh), but I want to do something with the children array only when all the ajax calls are done. Otherwise I'm obviously dealing with an incomplete array.
I have been looking at some jQuery solutions such as Deferred objects (using $.when().then() and such), but that would only solve the problem if I would not have the foreach-loop (as far as I can tell).
Also, changing the REST API (where the ajax calls are going) is not an option unfortunately, due to specified requirements regarding the API.
Ok, so without further ado: can anyone of you geniuses help me with this? :-)

ajax is asynchronous by default but you can turn it off. Here goes the API on how to do it
https://api.jquery.com/jQuery.ajax/
heres a little demp
$.ajax({
url: my_url.php,
type: "POST",
async: false,
dataType: 'json'
});
Or just make your next ajax call in a success function (Recommended)
function testAjax(handleData) {
$.ajax({
url:"getvalue.php",
success:function(data) {
//next ajax call here
}
});
}

You must run ajax query when previous query is completed with success (in jQuery onSuccess callback)

I had a smiler issue... below is a simplified version of my solution.
Step one: Declare global variables.
var results1,
results2,
[resultsN];
Step two: Make a function that accepts the results of each AJAX call as parameters.
function foo(results1, results2, [resultsN]) {
if (results1, results2, [resultsN]) {
//... do whatever you want with all of your results
}
}
Step three: Call all of the AJAX functions, set results to global variables, and call function foo for each.
function ajax() {
//AJAX call 1
$.ajax({
type: 'POST',
url: //URL,
success: function (data, textStatus, jqXHR) {
results1 = data;
},
dataType: 'json',
complete: function () {
foo(results1, results2);
}
});
//AJAX call 2
$.ajax({
type: 'POST',
url: //URL,
success: function (data, textStatus, jqXHR) {
results2 = data;
},
dataType: 'json',
complete: function () {
foo(results1, results2);
}
});
};
This method has the advantage of running as fast as the longest AJAX call takes. If you simply nest AJAX queries in the complete event then you will have to wait for each AJAX call to complete before moving to the next one...

how to use properties and methods withing a JavaScript class to exchange data?

i have small issue with exchanging data in between methods in a JavaScript object (class):
var TEST = (function () {
var TEST = function() {
};
TEST.prototype.get = function() {
$.ajax({
type: "GET",
url: "http://test.com/getall",
dataType: "json",
success: function (data) {
return data; // if i console log this i will get a json obj
}
});
};
TEST.prototype.parse = function(data) {
$.each(this.get(), function(k, v){
console.log(v);
});
};
return TEST;
})();
so i am trying to call one method in the each statement in another method. the issue is that
the response is undefined.
i also tried it like this, but with he same result
var testing = new TEST();
var get = testing.get();
testing.parse(get);
What am i missing? how can i return the data from this.get to be used in this.parse.
thanks

$.ajax() per default is asynchronous. That means, that the execution of your function get() wont wait until the request is finished. Hence you return no value from it, which results in undefined being returned.
In order to have your get() function be able to return a value, you would have to do the request in a synchronous way and set a variable in the outer function (as success itself is just another function, whose return value is not caught):
TEST.prototype.get = function() {
var result;
$.ajax({
type: "GET",
url: "http://test.com/getall",
async: false, // this is the important part!
dataType: "json",
success: function (data) {
result = data;
}
});
return result;
};
EDIT
As mentioned by #pebbl, this will halt the execution of all your scripts, until the request is done. Hence your whole page will be blocked for the time being.
The general approach is to use callbacks in such cases, which will be executed once the requests finished. So in your case something like this:
TEST.prototype.get = function( cb ) {
$.ajax({
type: "GET",
url: "http://test.com/getall",
dataType: "json",
success: function (data) {
cb( data );
}
});
};
with later on calling like this:
var testing = new TEST();
testing.get( function( data ) {
testing.parse( data );
});

You can't construct your function this way as you are relying on an asyncronous call, which will return it's result outside of the normal execution flow. The only way you can actually receive the result of your .get function is to use a callback.
Put simply your value isn't being returned from the .get function, it's being returned from the callback you are passing into jQuery's .ajax method.
You'd be far better off redesigning your code so as to still support the asyncronous call -- rather than disabling async.
A rough idea is to change your parse function like so:
TEST.prototype.parse = function(data) {
this.get(function(result){
$.each(result, function(k, v){
console.log(v);
});
});
};
And to change your get function accordingly:
TEST.prototype.get = function(callback) {
$.ajax({
type: "GET",
url: "http://test.com/getall",
dataType: "json",
success: callback
});
};
The above is just a quick example, you'd be wise reading up on the following jQuery topics:
http://api.jquery.com/promise/
http://api.jquery.com/category/deferred-object/
If you design your code around the promise pattern you'll find it complicated at first, but it gives you a lot of power in your code -- and gets around the whole callback stacking madness you can end up with when dealing in ajax calls.
Whilst it's not entirely clear from the jQuery.ajax documentation, this function returns a jqXHR object which implements the promise interface. So this means you can use the promise methods done, always and fail.
http://api.jquery.com/jQuery.ajax/

jquery trouble with getJSON call

Got some basic problem again.
I need to modify a function that previously returned a in code written object.
Im now trying to get the object from json through $.getJSON
function getEventData() {
var result = '';
$.getJSON("ajax.php?cmd=getbydate&fromdate=&todate=", function(data) {
result = data;
});
return result;
}
Problem is that result isn't set in the callback function for obvious reasons.
Do you guys have a solution for this?
Edit:
Ok i got an answer that was removed.
I just had to change it abit..
This is the answer that works:
function getEventData() {
var result = '';
url = "ajax.php?cmd=getbydate&fromdate=&todate=";
$.ajax({
url: url,
async: false,
dataType: 'json',
success: function(data) {
result = data;
}
});
return result;
}

You should program your application in an asynchronous way, which means, that you should use callback functions for you application flow, too, or continue in the getJson callback function. You can also make the request synchronously which should then be able to return the value (or at least assign it and block the function till the callback is completed), but this is not recommended at all:
function getEventData() {
var result = '';
result = $.ajax({
url: "ajax.php?cmd=getbydate&fromdate=&todate=",
async: false,
dataType: "json",
data: data,
success: function(data) {
return data;
}
});
return result;
}

Are you sure that the server returns valid json? It will be better to validate it using a tool like jsonlint. Also make sure that application/json is used as content type for the response.

Using Jquery to get JSON objects from local file

I'm trying to get a list of JSON objects (products) from a local file using Jquery and store all the objects in a single array called allItems. The file is co-located in the same directory as the code, and it's called "allItems.json". Here's how I'm doing it now:
function getAllSupportedItems(){
var allItems = new Array();
$.getJSON("allItems.json",
function(data){
$.each(data.items,
function(item){
allItems.push(item);
});
});
return allItems;
}
Based on this example: http://api.jquery.com/jQuery.getJSON/

For getAllSupportedItems to be able to return any items, the AJAX call needs to run synchronously.
getJSON translates to the following asynchronous call:
$.ajax({
url: url,
dataType: 'json',
data: data,
success: callback
});
Asynchronous is the default. You therefore need to explicitly change your request to a synchronous one:
$.ajax({
url: url,
dataType: 'json',
data: data,
success: callback,
async: false
});
An alternative is to rethink the way you use getAllSupportedItems and make it into an asynchronous utility:
function getAllSupportedItems(callback){
$.getJSON("allItems.json",
function(data){
var allItems = [];
$.each(data.items,
function(item){
allItems.push(item);
});
callback(allItems);
// callback(data.items); should also work
});
}
Update
When I initially wrote this answer, jQuery didn't have built-in Deferred support. It is a lot more concise and flexible to do something like this today:
function getAllSupportedItems( ) {
return $.getJSON("allItems.json").then(function (data) {
return data.items;
});
}
// Usage:
getAllSupportedItems().done(function (items) {
// you have your items here
});

How are you using this? If you're expecting the main function ("getAllSupportedItems") to return the array you make, well that won't work. The $.getJSON function is asynchronous, and so the handler won't actually build the array until after the outer function has returned.