We Keep Coding

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

javascript assignment of a string issue [duplicate]

This question already has answers here:
How do I return the response from an asynchronous call?
(41 answers)
Closed 9 years ago.
Im having an issue assigning a string to a variable and then returning it. It sounds simple and should be but im completely lost as to why what is happening is happening.
My code:
function drawpills() {
var picid;
$.post('js/fetchdata.php', function (data) {
var clock = document.getElementById('clock');
clock.innerHTML = "<img src='images/clock/pill.png' alt='pill_image' id='pillpic" + data + "'/>";
picid = "pillpic" + data;
alert(picid); //if i run it here i get pillpic31 which is what i want
});
alert(picid); //if i run it here i get undefined which is not what i want and which is what is being returned
return picid;
}
I highlighted the issue with comments on the respective line. Any help is appriecated.

Suggest you read through the linked article in comments.
What you need is something like this:
function drawpills(callback){
var picid;
$.post('js/fetchdata.php', function(data){
var pcid = data; // process pcid here
callback(pcid);
});
}

The problem is the asynchronous behavior of AJAX. When the AJAX response is sent, it moves onto the next statement, whether or not the call has finished executing. You can now do one of two things. You could either make the AJAX synchronous, which will probably break the timing of events on the page, or you could create a callback to be executed when the AJAX call is completely finished.

$.post callback is asynchronous function,so:
function drawpills(){
var picid;
var callback = function(data){
var clock = document.getElementById('clock');
clock.innerHTML="<img src='images/clock/pill.png' alt='pill_image' id='pillpic"+data+"'/>";
picid="pillpic"+data;
alert(picid);
}
$.post('js/fetchdata.php', callback);
//picid is undefined,because callback is running until server response data.
//unless you using synchronous request
alert(picid);
return picid;
}

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

Javascript Scope: variable not defined [duplicate]

This question already has answers here:
How to return AJAX response Text? [duplicate]
(2 answers)
How do I return the response from an asynchronous call?
(41 answers)
Closed 9 years ago.
In the following code the alert inside the function works fine, but the second has variable undefined, and yet I have delcared the variable outside of the function. Why is this?
var data = [];
$.post(
'matchEngine.php',
function(data) {
for (var i = 0, len= data.length;i <len; i++) {
for ( h = 0, len2= data[i].length;h <len2; h++) {
data[i][h][0]=(data[i][h][0])*30;
data[i][h][1]=(data[i][h][1])*30;
data[i][h][3]=data[i][h][3].replace(/\"/,"");
}
}
alert(data[0][0][0]);
}
);
alert(data[0][0][0]);
if you are suffering a similar problem the following How to return the response from an AJAX call? has the definitive explanation and answer.

The reference data in the function parameter and outside the function are different variables. In first case, it is in global scope, and in the second it in the local scope..They are completely different.
The example illustrates the issue....
var data=2;//this
function fun(data){ //and this are different
alert(data);
}
var data2=3;
fun(data2);

You can try this:
var data = [];
var myRequest = $.post(
/* your stuff */
);
myRequest.done(function() { alert(data[0][0][0]); })

As pinkpanther noted, the local data variable inside your $.post callback is not the same variable as the data variable outside the function.
Additionally, since $.post is asynchronous, you need to either pass it a callback or use the deferred object that it returns to access the response.
$.post('matchEngine.php').then(function(data){alert(data)})
for example, if you want to be able to pass the response around to other functions, you can do something like:
function doPost(url){
return $.post(url);
}
function processResponse(response) {
alert(response);
}
responsePromise = doPost("matchEngine.php");
responsePromise.then(processResponse);
As an aside, I recommend using $.ajax instead of $.post if you are going to use the callback style instead of promises. The reason being that $.ajax provides an error callback while $.post does not.

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);
});