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Callback timing issue in javascript when passed through view in asp mvc

I have a feeling this is a simple issue I'm missing but after a couple of hours I've given up and decided to post in here.
I'm trying to implement a generic paging partial view that I can use across the entire site. As a result the paging model takes a function that will be bound to the paging controls that is used as a callback at a later time. See UpdateFunction below.
ViewModels.Shared._PaginationPartialViewModel pagination =
new ViewModels.Shared._PaginationPartialViewModel()
{
CurrentPage = Filter.Page,
ItemFrom = GenericHelpers.Paging_GetItemFrom(10, Filter.Page, TotalItems),
ItemTo = GenericHelpers.Paging_GetItemTo(10, Filter.Page, TotalItems),
TotalItems = TotalItems,
TableClass = Filter.Table,
TotalPages = (int)Math.Ceiling((double) TotalItems / 10),
UpdateFunction = "getTransfers('" + Filter.Table + "')"
};
Now when the model is bound to the view, this function is passed in as a callback to a javascript click event paginationClick() like so...
#Model.CurrentPage
The paginationClick() function fires, but when checking the dev console the callback method appears to be firing first. Here's the paginationClick() method... (I know that the page parameter is not currently being utilized btw!)
function paginationClick(control, page, callback)
{
if (!$(control).hasClass('stock-pagination__action_state_active')) {
$(control).parent().find('a').each(function () {
$(this).removeClass('stock-pagination__action_state_active');
});
$(control).addClass('stock-pagination__action_state_active');
callback;
}
}
I anyone can offer an extra pair of eyes it would be much appreciated!

I found a work around with this, instead of passing getTransfers in as a callback, I appended it to the control as a data-attribute then used eval to execute at the correct time like so:
data-callback="#Model.UpdateFunction"
and then
function paginationClick(control, page)
{
if (!$(control).hasClass('stock-pagination__action_state_active')) {
var arr_Controls = [];
$(control).parent().find('a').each(function () {
$(this).removeClass('stock-pagination__action_state_active');
arr_Controls.push($(this));
});
$(control).addClass('stock-pagination__action_state_active');
eval($(control).attr("data-callback"));
//callback;
}
}
It's not the solution I was after but it works. If anyone has any idea how to get it working as a callback please let me know.

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)
});

Appending new results to an open jQuery autocomplete menu

I have an app in which I have multiple search sources. Previously, the users had to choose in what source to search in before searching. If they did not choose, the app would default to one of the options.
However, now they want to search in all the sources at the same time. This is fine enough, but the problem is that when one of the searches returns, it overwrites the previous search result. Pretty much expected behavior. What I basically want is to append the new results to the already open autocomplete menu, instead of overwriting the old results. Naturally, the autocomplete menu would have to empty when it closes.
I guess that this is possible to do, but what approach is the best? I could just have an array I guess, which I append results to and then overwrite _renderMenu to use this array instead of the items one that is passed to the function. Then empty said array at the close event.
Is this the best way to go though? Or is there a more elegant solution?
Some code:
Ok, so searchAction is called by jquery autocomplete eventually. In collection.search I do the ajax call, here the URL is created based in the this parameter, then respondWhithData is called and maps the search result to a proper format (ie value and label for the autocomplete menu). After reponse is called from respondWithData, jquery automagically renders the resultsmenu. Thus, I probably have to overwrite the reponse event function as well as the _renderMenu and possibly _renderItem, yes?
searchAction: function(searchTerm, collection, response){
var self = this;
$.when(collection.search(searchTerm, this)).then(function(data) {
self.respondWithData(data, response);
});
},
respondWithData : function(data, response) {
if (data.length > 0) {
var responseVal = _.map(data, this.mapData);
this.checkResponseCount(responseVal);
response(responseVal);
}
else {
response(this.emptyResult());
}
},
To be clear, the problem is not the multiple search itself, but rendering the asynchronos results. I want to render the first results that come back, and then appends the rest as soon as they are returned from the server.
Edit 2:
Just tried to edit ui.content in the autocompleteresponse event, but any edit does not take once it renders for some reason...
Edit 3: Ah, ui.content can only be modified directly, not changed. If I push every single change instead of concating two arrays ui.content shows what I want.
It works I guess, but its not perfect.

I can figure how looks your scenario but I'm guessing:
You should have like:
function search1() {
$.ajax({ ...
success: function(data) {
$('#myResultsDiv").html(data)
}
});
}
etc
Instead of overwritting the #myResultsDiv you need to Append the results like:
function search1() {
$.ajax({ ...
success: function(data) {
$('#myResultsDiv").append(data)
}
});
}
Edit: You can also do something like this:
var resultsArray = [];
var searchDone = 0;
var totalSearchs = 5; //assuming 5 searches
function search1() {
function search1() {
$.ajax({ ...
success: function(data) {
//APPEND data to resultsArray
searchDone++;
if(searchDone==totalSearch) //syncronize the 5 searchs before render
renderSearchs(resultsArray);
}
});
}

How do you debug Timing Issues in Javascript?

I recently ran into a familiar javascript/jQuery timing bug and spent too long debugging it. What I need is a smarter debugging path for this problem.
In specific, my issue was that user inputs were supposed to be causing a Mongo database call and the results were sent, after a little math, to displayed outputs. But the displayed outputs were crazily wrong. However, once I added a FireBug break point the problem went away. At that point I knew I had a timing issue, but not how to solve it.
Here are the relavant pieces of code before the error:
handleDataCallBack : function(transport) {
var response = $.parseJSON(transport);
if(!hasErrors) { this.updatePage(response); }
},
accessDatabase : function(){
var params = { ... };
DAL.lookupDatabaseInfo(this.handleCallBackOutputPanel, this, params);
},
calculateValues: function() {
// some numerical values were updated on the page
}
onDomReady : function() {
// ...
//bind drop-down select change events
$('#someDropDown').change(function() {
me.accessDatabase();
me.calculateValues();
});
}
To fix the problem, all I had to do was move the "calculateValues" method from the onDomReady inside the call back:
handleDataCallBack : function(transport) {
var response = $.parseJSON(transport);
this.calculateValues();
if(!hasErrors) { this.updatePage(response); }
},
The problem was that the database hadn't responded before the calculations were started. Sure, that's easy to spot in retrospect. But what methods can I use to debug asynchronous timing issues in javascript/jQuery in the future? This seems well outside the context of IDE tools. And FireBug didn't help. Are there any tools for tracking down asynchronous web development issues? Or maybe some time-tested methods?

i assume your problem is caused here:
$('#someDropDown').change(function() {
me.accessDatabase();
me.calculateValues();
});
this issue is that your calculations are done just right after the call. seeing that the DB call is async, calculate does not wait for it. however, you can do it using "callbacks". i see you do try to implement it and yes, it is correct. however, i find this more elegant:
calculateValues: function() {
// some numerical values were updated on the page
},
//since this is your general callback hander
//you hand over the return data AND the callbackAfter
handleDataCallBack: function(transport, callbackAfter) {
var response = $.parseJSON(transport);
//you may need to use apply, im lost in scoping here
callbackAfter();
//or
callbackAfter.apply(scope);
if (!hasErrors) {
this.updatePage(response);
}
},
accessDatabase: function(callbackAfter) {
var params = {};
//pass callbackAfter to the function,
//after this is done, pass it to the handler
DAL.lookupDatabaseInfo(this.handleCallBackOutputPanel, this, params, callbackAfter);
},
onDomReady: function() {
$('#someDropDown').change(function() {
me.accessDatabase(function() {
//send over what you want done after.
//we'll call it "callbackAfter" for easy tracing
me.calculateValues();
});
});
}​

How do I call a function stored in a jQuery array?

I have an array of hooks in jQuery that are executed before I load data into a grid. In one case, however, I want to remove the hook, then add it back for later. Whatever I'm doing is not working just right... it's probably a syntax error because I'm still somewhat new to jQuery. Any help would be appreciated, thanks!
Current code:
var preLoad = this.opts.hooks.preLoad.pop();
//stuff happens
//now I want to add the preLoad hook back
this.opts.hooks.preLoad.push(function(report) { preLoad(report); });
EDIT
It turns out the issue lies elsewhere in the code. However, I'd still like to know how best to accomplish this.

You access it the same way as any other variable stored in any other array.
this.opts.hooks.preLoad[0](myReport)

Can you not just add the function you removed like this?
var preLoad = this.opts.hooks.preLoad.pop();
//stuff happens
//now I want to add the preLoad hook back
this.opts.hooks.preLoad.push(preLoad);
And are you sure it's always the last one in the array that you want to remove?

It probably has to do with the fact that you are "canning" the argument "report" when you push the function back on the stack.
Try doing it like that:
var preLoad = this.opts.hooks.preLoad.pop();
//stuff happens
//now I want to add the preLoad hook back
this.opts.hooks.preLoad.push(preLoad);
I've tested it here http://jsfiddle.net/fWRez/

The example you gave has nothing to do with jQuery and is pure Javascript. Also, beware that what you are doing in your example is... not right. Consider this :
var ReportManager {
...
replace: function(report) {
var preLoad = this.opts.hooks.preLoad.pop();
//stuff happens
//now I want to add the preLoad hook back
this.opts.hooks.preLoad.push(function(report) { preLoad(report); });
}
}
If you execute this :
replace(null);
replace({foo:'bar'});
replace(null);
Your this.opts.hooks.preLoad array will look like this :
Array(
0: function(report) { return function(report) { return function(report) { ... } } }
)
Because you are pushing the function wrapped into itself every time you execute your code. I'm not sure why you need to pop and push it back in again, but this just look odd.
Also, Javascript is a very flexible language; which mean that you can do many weird stuff, like
"hello".concat(" world"); // -> 'hello world'
0.toString(); // -> '0'
(function(a) { return a; })("foo"); // -> 'foo'
(function() { return false; })() || (function() { return true; })(); // -> true (executes both functions)
(function(i) { return [i*2,i*3,i*4]; })(2)[1]; // -> 6
$('selector')[0]; // ...
// etc.