Set variable inside AJAX callback function [duplicate] - javascript

This question already has answers here:
How do I return the response from an asynchronous call?
(41 answers)
Closed 9 years ago.
I need able or disable a click event depending on the server result. I have the following funcion using jquery:
$("#button").click(function(){
var validated = true;
$.ajax({
url: "/Foo",
type: "POST",
success:function(data){
// alert(validated); ----> true
if(data){
validated = false;
// alert(validated); ----> false
}
}
});
// alert(validated); ----> true
return validated;
});
In the above code, always return true. I think the problem is that I set wrong the global variable validated. I have read this post and this but does not work for me. What am I doing wrong?

The problem is, that the AJAX call happens in a separate "thread" than the rest of the function. Thus, the thread with the click event runs on its own, does the AJAX call which is done ASYNCHRONOUSLY, and then returns. The AJAX thread never has the time to modify the validated var - the click handler has already returned.
The best way to solve this would be to make a callback from within the AJAX thread, or disable the element you want inside the AJAX thread itself, rather than returning a result to another function, which will then modify your button in another thread.

Related

Get data asynchronously JavaScript within for loop [duplicate]

This question already has answers here:
How do I return the accumulated results of multiple (parallel) asynchronous function calls in a loop?
(5 answers)
Closed 6 years ago.
I have this function
function add_cnh(arr_clelem){
var id=arr_clelem.getElementsByClassName("present")[0].id;
var date=arr_clelem.getElementsByClassName("present")[0].getAttribute('date');
var tt_entry= arr_clelem.getElementsByClassName("present")[0].getAttribute('tt_entry');
//new Ajax.Updater('register', '/some_url', { method: 'get' });
new Ajax.Request('/attendances/new',
{
parameters:'id='+id+'&date='+date+'&timetable_entry='+tt_entry+'&subject_id='+subject_id,
asynchronous:true,
evalScripts:true,
method:'get'
/*onSuccess: function(transport) {
var response = transport.responseText || "no response text";
alert("Success! \n\n" + response);
}*/
}
)
var ret=modal_data;
// $$('.MB_close').invoke('observe', 'click', _deinit);
return ret;
}
This function takes html-elements-object as an argument and basically render a modal-box and that modal box contain a form -elements which i need to store inside an array. The variable modal_data contains the elements which I require and its a global variable define in another file.
My problem is
This is a very old project using many JavaScript frameworks and libraries which date back to 2006 the library responsible for opening the model box itself is deprecated as can be seen here
And somehow I don't want to get into server side so I am using a for loop something like this
for(var i=0; i<arr_of_elements.length, i++)
{
my_arrvar[i]=add_cnh(arr_of_elements[i]);
}
Now with each itteration since I want the modal box to get closed and store the data within 'my_arrvar' which is somehow not possible as the call is asynchronous in nature and I've used closures and callbacks but no success. I don't want to use any sort of timer. So this is how it goes
Call the function and get data for each call and remove the modal box by id.
Also can this be used somehow and if then how?
You have to pass in ajax request asynchronous:false instead of true. Otherwise its not possible by another way.
Other Way using jQuery
The easiest way is to use the .ajaxStop() event handler:
$(document).ajaxStop(function() {
// place code to be executed on completion of last outstanding ajax call here
});
See jQuery Event handler

jQuery: On Click Ajax return data but does show in alert on first call [duplicate]

This question already has answers here:
How do I return the response from an asynchronous call?
(41 answers)
Closed 8 years ago.
I have some jquery code. when a button clicked it is suppose to send a ajax call to the server controller action, fetch some data from there and return it into a 'DIV' with id 'note-popover'.
.on('click.notes', '.pd-notes', function (e) {
e.preventDefault();
$.post("a_a/pd_notes", function (data) {
$("#note-popover").html(data);
});
alert("Data Returned" + $("#note-popover").html());
});
I have tested this code in Chrome Development tool as well, on the first click, it make a call to the server, the alert content however shows empty even though in the DOM the 'DIV' is filled with returned data, however every consecutive call the alert seems to return the data in the alert.
I am new so this may be a stupid question. What is the reason for this behaviour and how to fix it.
Any help is appreciated
Thank you
The data is only valid inside the handler
.on('click.notes', '.pd-notes', function (e) {
e.preventDefault();
$.post("a_a/pd_notes", function (data) {
$("#note-popover").html(data);
alert("Data Returned" + $("#note-popover").html());
});
});
$.post is asynchronous and starts an operation and in your example returns immediately to your alert.
Later the data comes back to the callback function you provided to post.

Get Data out of JQuery Function $.getJSON [duplicate]

This question already has answers here:
Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference
(7 answers)
Closed 8 years ago.
This is more of a basic JQuery/Javascript question: How do I get data out of the getJSON function?
The following code works great until the function ends. I have several getJSON that will need to run one-after-the-other and I would like to avoid nesting them if I can:
//Using the Web API to pull all the information out for the current ORG ID
$.getJSON('http://localhost:8081/dhis/api/organisationUnits/' + vuCurrentFacilityID + '.json', function (data) {
//alert(data.message);
console.log(data);
vuCurrentFacilityName = data.name;
vuParentFacilityID = data.parent.name;
});
alert(vuCurrentFacilityName); //does not work
What Gotcha* am I missing?
This question is very similar to the following.
if you call $.getJSON() you are entering an asynchronous context, and everything after it gets executed immediately. So your alert is called before the server responds.
use deferreds instead
var promise = $.getJSON( ... );
promise.done(function() {
alert("yeah");
});

Making $.get assign something to a variable [duplicate]

This question already has answers here:
How do I return the response from an asynchronous call?
(41 answers)
Closed 9 years ago.
I'm trying to use $.get() to retrieve data from a server, and assign it to a variable to work with it. For example:
$.get('htmllink', {}, function(results){
//do stuff here
});
var morestuff = ; //$.get() data goes here
The problem is, I can't get anything to work outside the rounded brackets. Everything is treated as internal variables or something. What am I missing?
You need to do all of your processing inside the callback function. This is because the call to $.get only starts an asynchronous request, and then the next line (var morestuff = ...) is executed after the request starts, but before it has completed.
$.get('htmllink', {}, function(results){
//do stuff with results in here
});
The problem here is that the $.get request is asynch (Ajax), so there is a timing issue here. The
var morestuff =
will run before the Ajax call returns, so you won't have the value to assign.
You have to interact with the result of the ajax request in the call back to have access to it
$.get('htmllink', {}, function(results){
//all code that depends on results must run inside here
});
//you can't execute code here that depends on the Ajax call

Trying to use JSON value outside $.getJSON function [duplicate]

This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
JavaScript asynchronous return value / assignment with jQuery
I have the following javascript code, the time.php file has minute and hour output using json_encode function. If I move console.log inside the getJSON function it finds the correct values, however when I move it outside the function it shows as undefined.
var my_hour;
$.getJSON('../scripts/time.php', function(data) {
my_hour = data.hour;
});
console.log(my_hour);
The "$.getJSON" call is asynchronous; the interaction with the server takes time but the browser does not wait for it to finish. Thus, your code after the function call runs immediately, a long time before the callback runs.
it's because it's asynchronous. Ajax request made by $.getJson async call your script and variables my_hour is initialized after your console.log(my_hour).
If you want it to work that way, then you should put console.log in some setInterval.
http://www.w3schools.com/jsref/met_win_setinterval.asp
var interval = setInterval(function(){
if (my_hour != undefined){
console.log(my_hour);
clearInterval(interval);
}
}, 200);
But it's it's not a good practice anyway.., your code should be placed in callback function as mentioned above.
var my_hour;
$.getJSON('../scripts/time.php', function(data) {
my_hour = data.hour;
console.log(my_hour);
});

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