I am doing an AJAX call to replace everything below the header and everything above the footer of a the page when the user clicks a filter link.
The problem is that after the AJAX event, all the JavaScript events bound to the various DOM elements break. This makes sense as those were bound on a much lower module level example
$(".innerDiv").on("click",function(){doSomething();}
and by replacing the content of the parent container these events are no longer bound.
What is the correct way of handling this problem? I could add the event listener to a much higher level e.g
$(document).on("click",".innerDiv",function(){doSomething();}
But this would have the same inefficiencies and issues for which the live() function in jQuery was deprecated.
The other solution that I have found suggested is to rebind the events after the AJAX call. The problem is that this is a fairly complex page I am dealing with, and it contains a lot of JavaScript modules each of which have their own bindings. How would I keep track of every event that gets binded? Is there any way of accessing this information from within jQuery? should i be maintaining my own datastructure of all elements which have events bound to them?
Also would I need to unbind events using the "off()" function before making the AJAX request?
Thanks for your help
In JQuery could use beforeSend http://api.jquery.com/jQuery.ajax/ to unbind the events
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I'm currently trying to write what I feel like should be a very simple chrome addon using jquery. I have a tool I use for work that our IT department has stopped supporting Chrome with, because they have enough on their plate troubleshooting IE. Their solution however, was simply to remove the old onClick functions and added the property disabled="diabled" to all of our buttons.
My simple work around for this is using jquery to remove the disabled properly and append the onClick functionality. I've gotten this to work in a few instances, but the problem I'm running into is with new instances of buttons created using ajax forms.
Here's the code I'm currently trying to work with:
function restoreFunctionality() {
$("#RestoreDefaultsButton").removeProp("disabled").attr("onClick", "OnRestoreDeviceClientClick()");
}
RestoreFunctionality();
Now, this works fine for the initial load, however I'd also like this to work for every button that is to be created in the future. To do this, I added:
$("#RestoreDefaultsButton").on("restoreFunctionality", function(event) {
$("#RestoreDefaultsButton").removeProp("disabled").attr("onClick", "OnRestoreDeviceClientClick()");
});
This, however, does not work for me but also does not provide any sort of console error message telling me why it won't work. I can't seem to find an example of what I want. I see examples in the jquery doc where it can be called by clicking somewhere or something like that, however what I want is for it to just simply "work". Just look for new instances of that button ID and make the changes.
Is on() not the function I want to use in jquery 1.11.1? Am I somehow using this incorrectly? Any guidance to point me in the right direction would help.
Edit for clarification:
I am not trying to edit the same button multiple times in multiple locations. I am trying and willing to create code individually for each button that comes up, given I know the ID of each one.
Here is an example of something I have that is currently working:
The line of code for the button reads:
<input type="button" name="RestoreDefaultsButton" value="Submit"
id="RestoreDefaultsButton" disabled="disabled" class="aspNetDisabled InlineButtonStyle">
The code that I am using and that actually works just fine is now:
$("body").on("click", "#RestoreDefaultsButton", restoreDefaultFunctionality());
and restoreDefaultFunctionality() is simply:
$("#RestoreDefaultsButton").removeProp("disabled").attr("onClick", "OnRestoreDeviceClientClick()");
Again, the above code works just fine. What I seem to have trouble with is that not all of my buttons are present on load, I may click a link that loads a model on the same page/url with a form that has additional buttons. That button might read:
<input type="button" name="OpenToolkitButton" value="Submit" id="OpenToolkitButton" disabled="disabled" class="aspNetDisabled InlineButtonStyle">
Which is almost exactly the same as the original example, it's just been loaded after the script ran for the first time.
What I am looking for is a solution to make all individually specified buttons that I need, when they occur, to have that disabled removed and a specific onclick function added.
It appears that you have several things wrong and you are using .on() incorrectly.
First, ids in your document must be unique. You cannot have multiple DOM elements with the same id. That is both illegal HTML and will not correctly work with selectors. So, if you're trying to detect future "#RestoreDefaultsButton" objects in addition to the one you already have, you will have to change that because you can't have more than one and still have selector code work correctly. Usually, you want to use a class name instead of an id when you want to find multiple objects of the same type.
Second, your use of .on() is simply not correct. .on() allows you to register a callback function that will be called when a certain DOM event is triggered. So, when you do this:
$("#RestoreDefaultsButton").on("restoreFunctionality", fn);
You are asking for jQuery to call your function when the single "#RestoreDefaultsButton" object triggers the "restoreFunctionality" DOM event. Since "restoreFunctionality" is not a built-in DOM event, the only way that could ever trigger is if you triggered the event yourself.
The usual solution to modifying newly created objects that are inserted into the DOM is to go find the code that creates those objects and insert a function call (to call your own function that can find and "patch up" the newly created DOM objects right AFTER the newly created DOM objects have been created.
The newest browser versions allow you to register a callback to be notified when certain types of objects are added to the DOM so you could get notified automatically. These notifications are call MutationObservers (doc here). Unfortunately, those events are only implemented in the latest browsers (IE11) so you generally can't solely rely on them for a general web page.
Your click handler assignment could probably be solved with delegated event handling. In delegated event handling for dynamically created objects, you find a persistent object (that is not dynamically created) that will be in the parent chain of your dynamically created element and you bind the click event handler to that parent. Since click events "bubble" up the parent chain, the click event will be seen by the parent. Using the delegated form of .on() that works like this:
$("static parent selector").on("click", "dynamic element selector", fn);
You can then handle the event without worrying about the timing of when the dynamic element is created/destroyed, etc...
You can read more about delegated event handling in these references:
Does jQuery.on() work for elements that are added after the event handler is created?
jQuery .live() vs .on() method for adding a click event after loading dynamic html
jQuery .on does not work but .live does
Are you triggering the "restoreFunctionality" event after your ajax forms are built?
$("#RestoreDefaultsButton").trigger("restoreFunctionality");
Forces it to be synchronous if you have more to do after the call and before you finish the function
$("#RestoreDefaultsButton").triggerHandler("restoreFunctionality");
I understand that when you create a listener in jQuery Mobile like:
$('.this-class').on('swipe',tapHandler);
tapHandler will run twice. In order to eliminate this problem I have seen multiple solutions, such as:
$('.page-card').off('swipe').on('swipe',tapHandler);
or
wrapping it in side of pageinit in order to eliminate chaching issues if you are creating dynamic content within pagebeforeshow as seen here.
I also understand that even bubbling comes in to play here.
However, I was hoping that someone could explain why this known exists, and why the contributes to jQuery decided to take this route, knowing the drawbacks.
First lets discuss how jQuery Mobile works. Unlike normal web pages where jQuery is used jQuery Mobile uses ajax to load pages into the DOM, one or more pages can be loaded. Because of this, classic document ready is useless so jQM developers created page events.
Page events are major for this story. While document ready will trigger only one per page most of page events will trigger multiple times, depending on how much time page is re/visited.
Lets get back to on function (and all other similar functions like bind, delegate, deprecated live). Again when working on normal pages you will NEVER come to situation because same page will never stay in a DOM.
Here comes jQuery Mobile. If you are using a binding method inside a pageshow (or similar page event) that event will bind over and over. Basically on method was never intended to be used like this.
If you want to find out more about methods of prevention take a look at my other answer, look for topic: Prevent multiple event binding/triggering
I am developing a jQuery Mobile and PhoneGap app. I am using this code:
$('#contact').live('pageinit', function() {
//$.mobile.loading('show');
theme();
getData('contact/list',contactList);
//$.mobile.loading('hide');
});
When accessing page for the first time, it works good. In second attempt event is firing multiple times. I tried using bind but it doesn't work.
I think it is connected with live event. It is binded each time I initialize the page, which makes it multiple. Problem is solved when linking that way: window.location.href-it recreates DOM. Unfortunately I can't use it.
Is there any way to handle pageinit in another way?
I tried to find it earlier but with no success. Also looked at: click() firing multiple times
In theory, any event that can be bound by 'live' can be bound directly. The benefit of binding directly is that it will (iirc) overwrite the previous bound handler. As such, you would only have one handler, so it wouldn't get triggered multiple times on subsequent loading.
try something like:
$("#contact").pageInit(function() {
theme();
getData('contact/list', contactList);
});
I usually use the on() method instead of live() (which is now deprecated). I give each of my page containers an id, so on the index page it might be index, then I can bind to the event like:
$(document).on("pageinit", "#index", function() {
//do stuff here
});
Works same way for page show also.
When binding events in jquery mobile, you have to be very cautious as to ensure that they will not be bound multiple times. Navigating to a new page in jquery mobile will not "reset" the bound events as it would in more traditional navigation.
The issue your facing is most probably due to the function being bound to the event every time you access the page, meaning that the more you access the page, the more times you will get that function to be executed when you do.
In order to ensure the event is only bound once, I would recommend binding in the header of your initial page. This way, the event is bound once and for all, and the function will be run whenever this page is initiated.
You can try adding data-ajax="false" to any forms you are submitting that may be creating multiple versions of the page (firing events multiple times).
I have a grid and there is a column which contains <a> anchor tag with some additional information in <data-..> tag and has a class name <class='myspeciallink'>. And in my unobtrusive JS script I select all the elements with that class name and apply live('click'). I need that to be live() because the grid gets generated in the runtime.
What happens inside the live('click') handler? I use that additional data and add a <div> to the page based on that data. Which in its turn used to generate jQuery UI dialog. It works great on my computer.
But! How could that work in real-world? Should I be bothered about possible performance implications? I feel that applying live() on more than a dozen elements instantaneously
would affect the performance. Especially with rather complicated handler like mine - it needs to get the data, parse the data, create a div, apply a dialog and etc.
Does that smell like a bad design? Could you suggest a different approach or my concerns are unfounded? Can I use some sort of a profiler tool to find the bottlenecks in my javascript?
UPD: Still nobody suggested any profiling tool. firebug and chrome dev tools are good, but maybe there is something even better?
live("click") is actually better up-front from a performance standpoint: Instead of binding an event handler to each matched element, you're applying a single event handler which waits for events to bubble up and then sees if the element that triggered the event matches the selector .live was called on.
Compare this to $('selector').click(...) which does loop over each element and bind a new event handler. live('click') has no additional overhead regardless of how many page elements match its selector. Depending on how many elements your selector matches, using .live can avoid a delay of up to a few seconds during the initial load of each page.
However, the event handler must check each event which bubbles up against its selector, to see if there is a match. This is going to add a small amount of overhead to every click event, but chances are very good that your users will not notice the difference.
Peter bailey also has a nice post about this: Performance difference between jQuery's .live('click', fn) and .click(fn)
I'm dynamically adding a lot of input fields through jQuery but the page gets really slow when reaching 200+ inputs (think of the page like a html excel sheet). This is fine really because this scenario is not very common. However, when I dynamically remove the input fields from the page using jQuery's htmlObj.remove() function, the page is still slow as if there were hundreds of inputs still there. Is there any way to explicitly free memory in jQuery/javascript?
My experience with this is from using Firefox. When using Internet Explorer, the page is really slow from the start but that's a whole different story.
The technique I'm using is called event delegation as it's supposed to be the least memory resourceful approach, compared to having all handlers explicitly bound to every object on the page.
Sadly, blur and focus events do not work with event delegation and therefore I need to bind these to every input. This could possibly be the memory hog here. Also, in Firefox it seems I can't use checkboxes for 'changed' or 'key[down|up]' events in event delegation as these checkbox events do not bubble up to the document. Here binding explicitly too.
Anyone can share some experience with this? Can't really show a demo right now as the site has not been launched yet.
Thx.
read this, I'm sure it will help.