Develop Reference

Sequential AJAX call inside loop using jQuery.Deferred()

I'm having a loop, inside the loop there is an AJAX call. For each loop AJAX returns a value. I want sequential loop one after another only when AJAX request is completed. I've done this using async:false but this method hangs my other code.
I want to do with $.Deferred()
This is my code:
function CheckAvailability(Display) {
var Status = "";
$.ajax({
type: "POST",
url: "myurl",
dataType: "json",
data: { "Display": Display },
async: false,
success: function (result) {
Status = result[0].Availability;
}
});
return Status;
}
$(DisplayData).each(function (index, Display) {
var Availability = CheckAvailability(Display) === 'Yes' ? '' : '<span style="margin-left:10px"><i class="fa fa-exclamation text-danger"></i></span>';
var Name = Display.Name + Availability;
console.debug(Name);
});
I want output like:
Display1 Yes
Display2 No
Display3 No
Display4 Yes

Ajax Response add under each element

I have a question that I can't seem to answer about Jquery Ajax Response.
I use a for each to select some data from <p> tags in each info_div. This data I then use to do a ajax call to a service that replies with a XML. I want to place some elements from this XML under each div from where I took the two variables. Each div should have it's own reply.
$(document).ready(function () {
$('#action-button').click(function () {
$(".info_div").each(function () {
var var1 = $(this).find('p:nth-child(4)').text();
var1 = var1.slice(-10);
var var2 = $(this).find('p:nth-child(8)').text();
var2 = var2.slice(-1);
$.ajax({
type: "GET",
url: "http://www.mypage.com/mypage&value1=" + "va1" + "&value2=" + "var2",
cache: false,
dataType: "xml",
success: function (xml) {
$(xml).find('member').each(function () {
var name = $(this).find("title").text()
/* how do I get this variable under each $('.info_div') from where I selected the var1 and var2
Every attempt I made places all replies under all the divs in class .info_div */
});
}
});
});
});
});

I would not recommend you to send ajax requests in a loop. Better collect all your data, then send it to the server and handle the response.
Meanwhile, if you insist to do it in a loop, you should make a reference to the iterated element from $(".indo_div) collection, and use it in ajax callback.
$(".info_div").each(function() {
var _that = $(this);
var var1 = $(this).find('p:nth-child(4)').text();
var1 = var1.slice(-10);
var var2 = $(this).find('p:nth-child(8)').text();
var2 = var2.slice(-1);
$.ajax({
type: "GET",
url: "http://www.mypage.com/mypage&value1=" + "va1" + "&value2=" + "var2",
cache: false,
dataType: "xml",
success: function(xml) {
$(xml).find('member').each(function(){
var name = $(this).find("title").text()
that.append(name);
});
}
});
});

Returning Response in jquery ajax function

Getting problems in Response.d , based on the result which is returning by the checkusers() function I am saving the values. If the entered name is in already in database it should say "User already exists", if it is not in database it should create a new record.
But I am not getting the correct value from (response), I observed that Console.log(response.d) giving me correct values like 'true' or 'false'. I tried everything I know like-
changing async:"false"
var jqXHR = $.ajax({ and returning jqXHR.responseText
But none of they worked for me . Please help me with this.
submitHandler: function (form) {
var txtName = $("#txtName").val();
var txtEmail = $("#txtEmail").val();
var txtSurName = $("#txtSurName").val();
var txtMobile = $("#txtMobile").val();
var txtAddress = $("#txtAddress").val();
var obj = CheckUser();
if (obj == false) {
$.ajax({
type: "POST",
url: location.pathname + "/saveData",
data: "{Name:'" + txtName + "',SurName:'" + txtSurName + "',Email:'" + txtEmail + "',Mobile:'" + txtMobile + "',Address:'" + txtAddress + "'}",
contentType: "application/json; charset=utf-8",
datatype: "jsondata",
async: "true",
success: function (response) {
$(".errMsg ul").remove();
var myObject = eval('(' + response.d + ')');
if (myObject > 0) {
bindData();
$(".errMsg").append("<ul><li>Data saved successfully</li></ul>");
}
else {
$(".errMsg").append("<ul><li>Opppps something went wrong.</li></ul>");
}
$(".errMsg").show("slow");
clear();
},
error: function (response) {
alert(response.status + ' ' + response.statusText);
}
});
}
else {
$(".errMsg").append("<ul><li>User Already Exists </li></ul>");
$(".errMsg").show("slow");
}
}
});
$("#btnSave").click(function () {
$("#form1").submit()
});
});
checkusers function is:
function CheckUser() {
var EmpName = $("#txtName").val();
$.ajax({
type: "POST",
url: location.pathname + "/UserExist",
data: "{Name:'" + EmpName + "'}",
contentType: "application/json; charset=utf-8",
datatype: "jsondata",
async: "true",
success: function (response) {
console.log(response.d);
},
error: function (response) {
alert(response.status + ' ' + response.statusText);
}
});
}

Just because your database returns true or false doesn't mean this also gets returned by your CheckUser().
There are several options here:
Either you make a local variable in your CheckUser, Make your Ajax call synchronous, set the local variable to response.d in the success function and then return that local variable.
Another option is to work with Deferred objects and make your submithandler Ajax call wait for the Checkuser Ajax call to return;
A third option is to call your create ajax call from your success callback in your CheckUser Ajax call if the user isn't created yet.
I would recommend either option 2 or 3, because option 1 is not userfriendly.

I don't understand AJAX callbacks

I have a javascript function which executes on the change of a dropdown:
<script type="text/javascript">
$(function()
{
// Executes when the status dropdown changes value
$('select[name="status_dropdown"]').change(function(event)
{
var $this = $(event.target);
var orderId = $this.closest('tr').children('td:eq(0)').text(); // index 0 refers to the "order_id column" in the table
var result = null;
var scriptUrl = "ajax_php/update_status.php?order_id=" + orderId + "&status_id=" + this.value;
$.ajax(
{
url: scriptUrl,
type: 'get',
dataType: 'html',
async: false,
success: function(data)
{
result = data;
alert(result);
}
});
});
})
</script>
I am trying to get the alert call to show the return value of the following php code (which is true):
<?php
.
.
.
return true;
?>
The alert doesn't pop up. Anyone know why ???

I tried your code with another URL and it's working well.
There are three cases:
scriptUrl is not calculated properly and doesn't point to your PHP script
your server is down
you are accessing an URL not served under the same domain as the one of your script (same-origin policy)
You can see detail of your error if you add an error handler to ajax parameters :
error : function(jqXHR, textStatus, errorThrown) {
alert(errorThrown);
}

Return only returns a value within the php script - to output it to ajax you need to actually output the result to the page, in this case something like echo "true"; or print("true");

Try this
$(document).ready(function(){
$('select[name="status_dropdown"]').change(function(event)
{
var $this = $(event.target);
var orderId = $this.closest('tr').children('td:eq(0)').text(); // index 0 refers to the "order_id column" in the table
var result = null;
var scriptUrl = "ajax_php/update_status.php?order_id=" + orderId + "&status_id=" + this.value;
$.ajax(
{
url: scriptUrl,
type: 'get',
dataType: 'html',
async: false,
success: function(data)
{
result = data;
alert(result);
}
});
});
});

How to ensure that a function is executed completely, before navigating to another page?

I'm removing certain records using a webservice. The jquery ajax request is written in the onclick of a hyperlink. When im executing the script, line by line using firebug, it's getting removed otherwise it's not. Does any one meet any situation like this before? Please help
Code sample:
$(".target").click(function() {
func(); //This function should be executed completely before navigating to another page
});
var func = function() {
var items = $("#flag").find('td input.itemClass');
id = items[0].value;
var status = items[1].value;
var type = items[2].value;
var params = '{' +
'ID:"' + id + '" ,Type:"' + type + '" ,Status:"' + status + '"}';
$.ajax({
type: "POST",
url: "WebMethodService.asmx/DeleteItem",
data: params,
//contentType: "plain/text",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
$("#deleteNotificationMessage").val("Item has been removed"); // keep a separate label to display this message
}
//Event that'll be fired on Success
});
}

jQuery ajax functions return deferred objects, thus we return $.ajax. Then you should use deferred.done to execute the callback when the AJAX is fully finished. When the AJAX is done, navigate away using JS instead:
var func = function() {
...
return $.ajax({...}); //return our ajax deferred
}
$(".target").click(function() {
var target = this; //preserve "this" since this in the callback may be different
func().done(function(){ //our done callback executed when ajax is done
window.location.href = target.href; //assuming .target is a link
});
return false; //prevent the natural click action
});

You can use the async: false on the ajax call that is wait there to complete the call.
var func = function() {
var items = $("#flag").find('td input.itemClass');
id = items[0].value;
var status = items[1].value;
var type = items[2].value;
var params = '{' +
'ID:"' + id + '" ,Type:"' + type + '" ,Status:"' + status + '"}';
$.ajax({
type: "POST",
async: false,
url: "WebMethodService.asmx/DeleteItem",
data: params,
//contentType: "plain/text",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
$("#deleteNotificationMessage").val("Item has been removed"); // keep a separate label to display this message
}
//Event that'll be fired on Success
});
}
Alternative you can make the submit after the request.
$(".target").click(function() {
func(); //This function should be executed completely before navigating to another page
return false;
});
var func = function() {
var items = $("#flag").find('td input.itemClass');
id = items[0].value;
var status = items[1].value;
var type = items[2].value;
var params = '{' +
'ID:"' + id + '" ,Type:"' + type + '" ,Status:"' + status + '"}';
$.ajax({
type: "POST",
async: true,
url: "WebMethodService.asmx/DeleteItem",
data: params,
//contentType: "plain/text",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
$("#deleteNotificationMessage").val("Item has been removed"); // keep a separate label to display this message
$("#YourFormID").submit();
}
//Event that'll be fired on Success
});
}

Simply move the Event to the "success" handler in your ajax request:
$.ajax({
type: "POST",
url: "WebMethodService.asmx/DeleteItem",
data: params,
//contentType: "plain/text",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function(msg) {
$("#deleteNotificationMessage").val("Item has been removed");
//Event that'll be fired on Success
}
});
Alternatively use jQuery ajax callback methods.