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Struggling to call a Jscript function within jquery

I have a small MVC5/C# Web application. In short, users will select a location from a dropdown ("#UnitList"). This fires the jquery event, to populate the next dropdown ("#CheckItem") with a list of contacts associated to the location selected.
Being very inexperienced in Jscript and Jquery, I am lost.
Additionally, on the same event, I need to populate an element (hidden text box).
In order to fill the hidden elements, I use this code
$(function () {
$("[name='UnitList']").change(function () {
$("#DeliveryUnitID").val($(this).val());
});
});
To run the Jquery that populates the second dropdown:
$(document).ready(function() {
$("#UnitList").change(function() {
var batchId = $(this).val();
var urlForModesl = getURLBase() + "ICS_Requisitions/Details";
urlForModesl = urlForModesl + "/" + batchId;
var modelsHtml = "";
$('#CheckItem')
.find('option')
.remove()
.end()
.append('<option value="Select Contact"></option>')
.val('Contact')
$.ajax({
type: 'get',
url: urlForModesl,
contentType: 'application/json',
dataType: 'json',
success: function(jsonData) {
$.each(jsonData, function(key, value) {
modelsHtml += "<option value='" + value.LoginID + "'>" + value.ContactName + "</option>";
});
$("#CheckItem").html(modelsHtml);
$("#DeliveryUnitID").val($(this).val())
},
error: function(XMLHttpRequest, textStatus, errorThrown) {}
});
});
});
I am aware that I have two functions with the same name "$("#UnitList").change(function ()" and that this is very bad and causing conflicts. This is what I am trying to resolve.
I have tried to simply add the element update within the Jquery code, but that did not work.
I placed the following code
$("#DeliveryUnitID").val($(this).val())
Inside the Jquery, right after:
$("#CheckItem").html(modelsHtml);
But that does not work. The hidden elements are still empty.
I tried creating a function called foo, with the element update, and call that function from at the end of the jquery.
foo();
<script>
function foo() {
$("#DeliveryUnitID").val($(this).val());
}
That also left the element #DeliveryUnitID empty.
I know that I can't have two functions with the same name, but that's the only way I can get it working where the query populates the drop down, and then the hidden element is populated too. BUT . . . that's bad coding AND, for about 5% of the users, it fails.
I can't quite figure out how to make both happen with one onchange event.

It's been a while since I've used jQuery, so here's what I'm seeing:
On change Event:
Get the value of the #UnitList <select> (potential bug: these aren't being stored anywhere)
Clear the options
Re-populate with new ones from AJAX Request
Try to get value of new options (still within initial AJAX request, which might also be a bug? Like I said, it's been a while since I've used jQuery).
It looks like you might have a state-management issue?
Potential fixes:
Store values of first dropdown before you clear them.
Use the stored value to populate #DeliveryUnitID after the AJAX request
Use some if statements or remove the event listener to not constantly be running your code on change event once you get the data you need...unless you need it to be running constantly.
To me, it would seem beneficial (from a code pov and maybe also a UX perspective) to programmatically build a second dropdown to keep things clearer, but that might be overkill for what you're trying to accomplish.

Ajax call in "for" loops skips odd/even iterations

If I am here asking it is because we are stuck on something that we do not know how to solve. I must admit, we already searched in StackOverflow and search engines about a solution.. but we didn't manage to implement it / solve the problem.
I am trying to create a JavaScript function that:
detects in my html page all the occurrences of an html tag: <alias>
replaces its content with the result of an Ajax call (sending the
content of the tag to the Ajax.php page) + localStorage management
at the end unwraps it from <alias> tag and leaves the content returned from ajax call
the only problem is that in both cases it skips some iterations.
We have made some researches and it seems that the "problem" is that Ajax is asynchronous, so it does not wait for the response before going on with the process. We even saw that "async: false" is not a good solution.
I leave the part of my script that is interested with some brief descriptions
// includes an icon in the page to display the correct change
function multilingual(msg,i) {
// code
}
// function to make an ajax call or a "cache call" if value is in localStorage for a variable
function sendRequest(o) {
console.log(o.variab+': running sendRequest function');
// check if value for that variable is stored and if stored for more than 1 hour
if(window.localStorage && window.localStorage.getItem(o.variab) && window.localStorage.getItem(o.variab+'_exp') > +new Date - 60*60*1000) {
console.log(o.variab+': value from localStorage');
// replace <alias> content with cached value
var cached = window.localStorage.getItem(o.variab);
elements[o.counter].innerHTML = cached;
// including icon for multilingual post
console.log(o.variab+': calling multilingual function');
multilingual(window.localStorage.getItem(o.variab),o.counter);
} else {
console.log(o.variab+': starting ajax call');
// not stored yet or older than a month
console.log('variable='+o.variab+'&api_key='+o.api_key+'&lang='+o.language);
$.ajax({
type: 'POST',
url: my_ajax_url,
data: 'variable='+o.variab+'&api_key='+o.api_key+'&lang='+o.language,
success: function(msg){
// ajax call, storing new value and expiration + replace <alias> inner html with new value
window.localStorage.setItem(o.variab, msg);
var content = window.localStorage.getItem(o.variab);
window.localStorage.setItem(o.variab+'_exp', +new Date);
console.log(o.variab+': replacement from ajax call');
elements[o.counter].innerHTML = content;
// including icon for multilingual post
console.log(o.variab+': calling multilingual function');
multilingual(msg,o.counter);
},
error: function(msg){
console.warn('an error occured during ajax call');
}
});
}
};
// loop for each <alias> element found
//initial settings
var elements = document.body.getElementsByTagName('alias'),
elem_n = elements.length,
counter = 0;
var i = 0;
for(; i < elem_n;i++) {
var flag = 0;
console.info('var i='+i+' - Now working on '+elements[i].innerHTML);
sendRequest({
variab : elements[i].innerHTML,
api_key : settings.api_key,
language : default_lang,
counter : i
});
$(elements[i]).contents().unwrap().parent();
console.log(elements[i].innerHTML+': wrap removed');
}
I hope that some of you may provide me some valid solutions and/or examples, because we are stuck on this problem :(
From our test, when the value is from cache, the 1st/3rd/5th ... values are replaced correctly
when the value is from ajax the 2nd/4th .. values are replaced
Thanks in advance for your help :)

Your elements array is a live NodeList. When you unwrap things in those <alias> tags, the element disappears from the list. So, you're looking at element 0, and you do the ajax call, and then you get rid of the <alias> tag around the contents. At that instant, element[0] becomes what used to be element[1]. However, your loop increments i, so you skip the new element[0].
There's no reason to use .getElementsByTagName() anyway; you're using jQuery, so use it consistently:
var elements = $("alias");
That'll give you a jQuery object that will (mostly) work like an array, so the rest of your code won't have to change much, if at all.

To solve issues like this in the past, I've done something like the code below, you actually send the target along with the function running the AJAX call, and don't use any global variables because those may change as the for loop runs. Try passing in everything you'll use in the parameters of the function, including the target like I've done:
function loadContent(target, info) {
//ajax call
//on success replace target with new data;
}
$('alias').each(function(){
loadContent($(this), info)
});

ajax loading of search results

I have setup a search funtionality that will search in an XSLT file. This works flawlessly but I have a little trouble returning the search results dynamically with ajax.
This is my JS:
var SearchHandler = function(frm) {
frm = $(frm);
var data = frm.find(".search-field").val();
$.ajax({
method: 'GET',
url: '/',
data: { query: data },
dataType: 'xml',
success: SearchSuccessHandler,
error: SearchSuccessHandler
});
};
var SearchSuccessHandler = function(html) {
};
What I want is the SearchSuccessHandler to dynamically load the search result from index.php?query=searchword
I just can't seem to figure out the right way to handle it.

Based on your comment:
Bah.. Sorry... The ajax call will return some new html based on the
query ... I want the existing html to be replaced I have tried
$('body').html(html.responseText); but then I cannot search again
because javascript is not loaded correctly
It's not the AJAX which is the issue but rather event delegation
When you bind a function to an element directly like this:
$('.my-element').on('whatever', function() { ... })
the handler will work as long as the element exists however if you replace the contents of the entire body you'll run into trouble as your original .my-element no longer exists.
You can overcome that by using event delegation to make sure your function keeps searching e.g.
$(body).on('whatever', '.my-element', function() { ... })
This basically says: "If I click on body and the target is .my-element then execute this function"
Instead of a directly bound handler which says: "If I click on this specific element then execute this function"
the body will always exist and therefore you'll always be able to delegate down from the body but if you can do it on some more specific element that would obviously be better since then you won't have an onclick handler on the entire body.
I think this is what your issue is since you're replacing the entire body.

Try this
success:function(data) {
// do your stuff here
}
Of course, you need to be sure your function is returning some values.
To make it easier for your, encode the values as json on your index.php
return json_encode($values)
Then, inside your success function, just parse it with eval()

submitting a form via ajax upon stop event of jquery

UPDATE
Added this error, just says "Error caught"
<script type="text/javascript">
window.onerror = function() {
alert("Error caught");
};
xxx();
</script>
This is not working, I don't understand why.
My php script inserts data properly if called by itself without an if{method=post} statement
I tried with and without an if method = post argument on the php side to get the ajax below to work but I can't tell if the script is being called at all.
My aim is to submit the data without the user knowing, it's a coordinate / dimension update for a variable design interface.
This is my ajax insert which is supposed to work when a function is invoked after the stop is triggered eg. after an object is done moving which the function is invoked properly as I have set up sequential alerts to pop up after certain lines.
$("#form").submit(function(event){
event.preventDefault();
var $form = $( this ),
url = $form.attr( 'action' );
var posting = $.post( url, {
id: $('#id').val(),
name: $('#name').val(),
wname: $('#wname').val(),
xcor: $('#xcor').val(xcor),
ycor: $('#ycor').val(ycor),
xwid: $('#xwid').val(xwid),
yhei: $('#yhei').val(yhei),
photo: $('#photo').val(),
targeturl: $('#targeturl').val()
});
posting.done(function( data ){
alert('success');
});
});

This is wrong
xcor: $('#xcor').val(xcor),
ycor: $('#ycor').val(ycor),
xwid: $('#xwid').val(xwid),
yhei: $('#yhei').val(yhei),
Those object are holding jQuery objects, not a value.
Looks like you want to set the value and use the new value. This makes me cringe, but it would do the job
xcor: $('#xcor').val(xcor).val(),
ycor: $('#ycor').val(ycor).val(),
xwid: $('#xwid').val(xwid).val(),
yhei: $('#yhei').val(yhei).val(),
You would be better off updating them before the call and just using the variable when setting the object. Or just use jQuery serialize() and don't deal with grabbing the elements.

Prototype Event.observe not seeing AJAX-returned HTML

I'm trying to create a CMS system based on AJAX using Prototype's library. On a page load, I have HTML, page title and additional Javascript for the page returned via JSON, and I update the HTML on the main area. I also have an event listener that listens for certain ID's to be clicked on.
The listener is working,
var TabMenu = {
selectedTab: 'main',
showTab: function(pid) { alert(pid); alert($(pid));
$(pid).addClassName('selected'); this.selectedTab = pid;
$(this.defaultTab).removeClassName('selected');
}};
After loading, I click on one of the new tabs, and the first "test" alert successfully alerts the element's ID, but the second alert ($(pid)) returns null. I can only surmise that the HTML returned by the AJAX request is not being evaluated and added to the DOM, otherwise it would alert [HTMLDivElement] instead of "null".
Here is the relevant AJAX call:
new Ajax.Request(url, {
onSuccess: function(t) {
data = t.responseText.evalJSON();
Page.update(data.html, data.title, data.js);
Page.destroyLoader();
}
});
And here is the updating function:
update: function(data, title, js) {
document.title = Global.title + title;
if (title != "") { $('HEADING').update(title); }
$('MAIN').update(data);
if (js != "") {
var nuJS = new Element('script', { type: 'text/javascript' }).update(js);
$('MAIN').insert({ top: nuJS });
}
}
Any ideas on how I can get this working?

When is the ajax request triggered? Is it triggered when you click the tab? If so the showTab function is being triggered before data has been inserted into the DOM.
If you have firebug, try using the console to select the html data, after the ajax call has finished, to see what you get. You can also use firebug's html tab to see if the data has been inserted into the DOM.
Also, even though you get the pid parameter that is set to a value, does it refer to a real id that exists in the DOM?

From your code and the comment above.
I think your plan is to load all the tabs after the page loaded immediately.
And hide all of them using the css. Wait until the user click the tab,
Show only the one that is "selected", right?
That's mean you should change:
$('MAIN').update(data);
To something like
$('MAIN').update({after: data});
So it won't overwrite the existed one.
And don't forget to move the code for document.title and eval js into showTab function.
For javascript evaluation you can insert the js into data.html and use this instead:
$('MAIN').innerHTML.evalScripts();