I want this webpage to highlight certain elements when you click on one of them, but if you click anywhere else on the page, then all of these elements should no longer be highlighted.
I accomplished this task by the following, and it works just fine except for one thing (described below):
$(document).click(function() {
// Do stuff when clicking anywhere but on elements of class suggestion_box
$(".suggestion_box").css('background-color', '#FFFFFF');
});
$(".suggestion_box").click(function() {
// means you clicked on an object belonging to class suggestion_box
return false;
});
// the code for handling onclicks for each element
function clickSuggestion() {
// remove all highlighting
$(".suggestion_box").css('background-color', '#FFFFFF');
// then highlight only a specific item
$("div[name=" + arguments[0] + "]").css('background-color', '#CCFFCC');
}
This way of enforcing the highlighting of elements works fine until I add more html to the page without having a new page load. This is done by .append() and .prepend()
What I suspected from debugging was that the page is not "aware" of the new elements that were added to the page dynamically. Despite the new, dynamically added elements having the appropriate class names/IDs/names/onclicks ect, they never get highlighted like the rest of the elements (which continue to work fine the entire time).
I was wondering if a possible reason for why my approach does not work for the dynamically added content is that the page is not able to recognize the elements that were not present during the pageload. And if this is a possibility, then is there a way to reconcile this without a pageload?
If this line of reasoning is wrong, then the code I have above is probably not enough to show what's wrong with my webpage. But I'm really just interested in whether or not this line of thought is a possibility.
Use .live to "Attach a handler to the event for all elements which match the current selector, now and in the future". Example:
$(".suggestion_box").live("click", function() {
// means you clicked on an object belonging to className
return false;
});
Also see .delegate, which is similar.
Since the .live() method handles events once they have propagated to the top of the document, it is not possible to stop propagation of live events. Similarly, events handled by .delegate() will always propagate to the element to which they are delegated; event handlers on any elements below it will already have been executed by the time the delegated event handler is called.
from the jQuery documentation =)
(only to explain better why #karim79 also suggested the delegate method ;P )
Related
So I'm appending a row in a table and then upon clicking a button I want to remove that row.
However I can't do it in a way that seems natural, like:
$(".usun").on("click", function(){
$(this).parent().parent().remove();
});
where .usun is a class of buttons that remove a row in a table. Of course this fragment of code is inside of $(document).ready(.... What seems to work for me is this:
$(this).on("click", ".usun", function(){
$(this).parent().parent().remove();
});
and I don't understand why. Could someone explain me this?
There are several method signatures available for .on() which you can read about here.
Your first syntax ($(".usun").on() is, just one time, attaching click handlers to each individual .usun element. If more are added later, they don't have click handlers.
The second syntax ($(this).on("click", ".usun", function()...) attaches a single listener to the document, saying "any time a .usun inside me is clicked, do something". This covers a case where more matching elements are added after $(document).ready is fired.
That is because that specific .usun does not exist yet when you are registering the event.
You need to register the event to its parent element (prefereably the table id) like so:
$('#yourtableid').on("click", ".usun", function(){ //if table id does not exist, you can use $('body') instead
$(this).parent().parent().remove();
});
This will make sure that you are attaching the events even to 'unborn' elements.
Hope this helps!
So you're aware of this... your question is related to live and non-live lists (collections) in javascript;
review the following Javascript,
var queryStatic = document.querySelectorAll(".usun"); //non-live | static list
var queryLive = document.getElementsByTagName("div"); //live list
queryStatic will return a NodeList that statically references the nodes that satistifed the condition of the query.
If you were to alter/modify the properties/fields/members of a node or it's element that is referenced by this NodeList outside of using the queryStatic, it would be represented in the queryStatic instance;
you cannot, however, add a new element/node to the DOM that would have satisfied the query and expect it to be in that NodeList.
queryList (an HTML Collection), however, will represent both aspects. It is a live list.
The point is, the underline concept has little to nothing to do with method signatures.
Edit
However, in the case of jQuery's .on() method; there is support for attaching the listener to a parent element (like Document) and specifying an additional query criteria.
Here's an example http://jsbin.com/ukoqud/3/edit
If you click on a red box, you'll get an alert.
If you click on a link, everything in a blue box will be replaced with just a red box. Link will disappear and if you click on a red box then, you'll get no alert.
Why this happens?
Is it related to innerHTML?
Does it work the same way in all browsers?
Here's one more example http://jsbin.com/ukoqud/1/edit In this one you'll get an alert after clicking on a link. Things happen in a quite similar way, but result is different.
I would like to understand the reason, there's no need to fix my code.
When you call $(".red"), it returns a collection of DOM elements that exist at that moment. So $(".red").click(function...) just binds a handler to the click event on those elements. If you later create new elements with the same class, they weren't in this collection, so they don't have the handler bound to them. jQuery doesn't watch the DOM for changes and update the handlers dynamically -- the bindings are just on the elements you matched at the time you called click().
You either need to bind the handler again after adding the new HTML, or use delegation with .on():
$(".blue").on("click", ".red", function(){
alert('click on a red box detected');
});
This works by binding a handler to $(".blue"), which doesn't change dynamically. The handler checks whether the element you clicked on matches the ".red" selector, so it's able to handle dynamically-added elements without requiring rebinding.
I think the reason why it works in your second example is because the red block isn't inside the blue box to start. When you move it inside, jQuery reuses the same DOM elements, so the bindings go along with it. In the first example, the red box starts out inside the blue box. When you do $('.red').parent().html(...), the first thing it does is empty $('.red').parent() (the blue box), so the original red element is removed from the DOM, and its bindings are lost.
We need to understand how setting html of an element works. Then you will figure out your answer yourself.
Take a look at this bin Updated Bin
When we set HTML of an element, it first removes all the elements inside it.
Those elements are not removed from memory depending upon whether they are garbage collected or not.
If any of the child is having a reference, then that particular child won't be garbage collected.
In your case, we are having a reference to red element so it is still present in memory but not a part of document.
When we say blue.html(red) in my example, red element becomes a part of document again but this time there won't be any handlers on it So your click does not work.
While in your example2,
red element is always a part of document hence no handlers were lost when red element is moved inside blue element.
I hope this will help.
because when u click the link, you delete everything on screen and create everything from a scratch and event binding goes away. so you should use this
$(".blue").on("click", ".red", function(){
alert('');
});
this way, binding is done differently. it doesnt bind it statically
I've got a page with some Javascript / jQuery stuff, for example:
(function()
{
$('.tip').tooltip();
$('.test').click(function()
{
alert('Clicked!')
});
}();
On the page I insert some HTML with jQuery so the DOM changes. For example, I insert a extra element with the class "tip" or "test". The just new inserted elements doesn't work because jQuery is working with the non-manipulated DOM and the just inserted elements aren't there. So I've searched around and came to this solution for the "click":
$('body').on('click','.click',function()
{
alert('Clicked!')
});
I don't understand why, but this way it's working with the manipulated DOM and the jQuery stuff works on the new inserted elements. So my first question is, why does this work and just the click() function not? And the second question, why do I have to point to the "body"?
Finally, my third question is, how get this done with the tooltip?
I know that there is so many information about this subject (previous the delegate() and live() function I've read) but I can't found a explanation about it. And I can't get my third question solved with the information I found.
I'm looking forward to your responses!
Extra question:
4) Is it recommended to point always to the "body" for this kind of situations? It's always there but for possible performance issues?
So my first question is, why does this work and just the click()
function not?
Because the event handler is now delegated to a parent element, so it remains even after replacing/manipulating child elements.
Ancient article on event delegation for your perusal - but the concepts remain the same:
http://www.sitepoint.com/javascript-event-delegation-is-easier-than-you-think/
And the second question, why do I have to point to the "body"
You don't, any suitable parent element will do. For example, any direct parent (a div wrapper, for instance) which does not get replaced.
Finally, my third question is, how get this done with the tooltip?
You need to re-initialize your tooltip plugin on the newly inserted elements. For example:
$.get("foo.html", function (html) {
$("#someDiv").html(html);
$("#someDiv").find(".tip").tooltip();
});
The click() event doesn't work when you manipulate the DOM because JQuery is not watching for DOM changes. When you bind the click() event it is selecting the elements that are on the page at that time. New ones are not in the list unless you explicitly bind the event.
Because you have pointed the click() event on the body. JQuery then checks to see if the target of the click matches any of the event handlers (like what you have created) match the element clicked. This way any new elements will get the event 'associated' with them.
Because the tooltip isn't an event that you can place on the body, you will need to re-initialize it when the element is created.
EDIT:
For your fourth question, is it depends. The advantage of binding to the body is that you don't accidentally bind an event to an element more than once. The disadvantage is that you are adding event handlers that need to be checked on each event and this can lead to performance issues.
As for your concerns about DRY, put the initialization of the tooltips into a function and call that when you add them. Trying to avoid having the same function call is a little overkill in this regard, IMO.
Events are bound to the specific object you are binding it to.
So something like $('.tip').tooltip() will perform the tooltip() functionality on $('.tip') which is actually just a collection of objects that satisfies the css selector .tip. The thing you should take note of is, that collection is not dynamic, it is basically a "database" query of the current page, and returns a resultset of HTML DOM objects wrapped by jQuery.
Therefore calling tooptip() on that collection will only perform the tooltip functionality on the objects within that collection, anything that was not in that collection when tooltip is called will not have the tooltip functionality. So adding an element that satisfies the .tip selector, after the tooltip() call, will not give it the tooltip functionality.
Now, $('body').on('click','.click', func) is actually binding the click event to the body tag (which should always exist :P), but what happens is it captures whether the click event has passed through an element your target css selector (.click in this case), so since the check is done dynamically, new elements will be captured.
This is a relatively short summary of what's going on... I hope it helped
UPDATE:
Best way for your tooltip thing is to bind tooltip after you have added elements, e.g.
$('#container').load('www.example.com/stuff', function() {
$('.tip', $(this)).tooltip();
});
I have web layout, which can contains several links on it. Those links are dynamically created, using AJAX functions. And it works ok.
But, I don't know how can I work with those "dynamically created links" (ie. how to call some JS or jQuery function if I click on them). I guess that browser can not recognize them, since there are created after page is loaded.
Is there some function, that can "re-render" my page and elements on it?
Tnx in adv on your help!
You can use the 2 following methods jQuery provides:
The first one, is the .live() method, and the other is the .delegate() method.
The usage of the first one is very simple:
$(document).ready(function() {
$("#dynamicElement").live("click", function() {
//do something
});
}
As you can see, the first argument is the event you want to bind, and the second is a function which handles the event. The way this works is not exactly like a "re-rendering". The common way to do this ( $("#dynamicElement").click(...) or $("#dynamicElement").bind("click", ...) ) works by attaching the event handler of a determinate event to the DOM Element when the DOM has properly loaded ($(document).ready(...) ). Now, obviously, this won't work with dynamically generated elements, because they're not present when the DOM first loads.
The way .live() works is, instead of attaching the vent handler to the DOM Element itself, it attaches it with the document element, taking advantage of the bubbling-up property of JS & DOM (When you click the dynamically generated element and no event handler is attached, it keeps looking to the top until it finds one).
Sounds pretty neat, right? But there's a little technical issue with this method, as I said, it attaches the event handler to the top of the DOM, so when you click the element, your browser has to transverse all over the DOM tree, until it finds the proper event handler. Process which is very inefficient, by the way. And here's where appears the .delegate() method.
Let's assume the following HTML estructure:
<html>
<head>
...
</head>
<body>
<div id="links-container">
<!-- Here's where the dynamically generated content will be -->
</div>
</body>
</html>
So, with the .delegate() method, instead of binding the event handler to the top of the DOM, you just could attach it to a parent DOM Element. A DOM Element you're sure it's going to be somewhere up of the dynamically generated content in the DOM Tree. The closer to them, the better this will work. So, this should do the magic:
$(document).ready(function() {
$("#links-container").delegate("#dynamicElement", "click", function() {
//do something
});
}
This was kind of a long answer, but I like to explain the theory behind it haha.
EDIT: You should correct your markup, it's invalid because: 1) The anchors does not allow the use of a value attribute, and 2) You can't have 2 or more tags with the same ID. Try this:
<a class="removeLineItem" id="delete-1">Delete</a>
<a class="removeLineItem" id="delete-2">Delete</a>
<a class="removeLineItem" id="delete-3">Delete</a>
And to determine which one of the anchors was clicked
$(document).ready(function() {
$("#links-container").delegate(".removeLineItem", "click", function() {
var anchorClicked = $(this).attr("id"),
valueClicked = anchorClicked.split("-")[1];
});
}
With that code, you will have stored in the anchorClicked variable the id of the link clicked, and in the valueClicked the number associated to the anchor.
In your page initialization code, you can set up handlers like this:
$(function() {
$('#myForm input.needsHandler').live('click', function(ev) {
// .. handle the click event
});
});
You just need to be able to identify the input elements by class or something.
How are these links dynamically created? You can use use the correct selector, given that they are using the same class name or resides in the same tag, etc.
consider the html form
<form>
<input type="text" id="id" name="id"/>
<input type="button" id="check" name="check value="check"/>
</form>
jquery script
$('#check).click(function() {
if($('#id).val() == '') {
alert('load the data!!!!);
}
});
here on clicking the button the script check the value of the textbox id to be null. if its null it will return an alert message....
i thin this is the solution you are looking for.....
have a nice day..
Noramlly , the browser process response HTML and add it to DOM tree , but sometimes , current defined events just not work , simply reinitialize the event when u call the ajax request ..
All you need to do to work with dynamically created elements is create identifiers you can locate them with. Try the following code in console of Firebug or the developer tools for Chrome or IE.
$(".everyonelovesstackoverflow").html('<a id="l1" href="http://www.google.com">google</a> <a id="l2" href="http://www.yahoo.com">yahoo</a>');
$("#l1").click(function(){alert("google");});
$("#l2").click(function(){alert("yahoo");});
You should now have two links where the ad normally is that were dynamically created, and than had an onclick handler added to bring up an alert (I didn't block default behaviour, so it will cause you to leave the page.)
jQuery's .live will allow you to automatically add handlers to newly created element.
If your links are coming in via AJAX, you can set the onclick attributes on the server. Just output the links into the AJAX like this:
Holy crap I'm a link
The return false makes sure the link doesn't reload the page.
Hope this helps!
I'm trying to build a greasemonkey script which will dynamically create tables of data based on user interaction with... other dynamically created tables of data. My problem is that I'm having to make two passes every time I create a table: one to create the table, and another to go grab all of the objects in the table I want to add event handlers to (by id) and add the various event handlers to them.
If I attempt to, say, add an onClick event to a table td before I've created the table and inserted it into the HTML, I get a "component is not available" exception.
This is incredibly cumbersome, because I either have to maintain, separately, a list of the ids and what I should do to those elements when I make my second pass to add the handlers, or develop a naming convention by which I know, based on the id, what I should do with the element.
There HAS to be a better way to do this. I just haven't figured it out yet. Anyone have any ideas?
Firstly, I'd love to know why you need a different ID for every single TD. Is the ID holding important information, such as an index? In this situation it might be better creating each TD within a loop. Also, obviously you can't attach an event handler to a DOM element which doesn't exist! It doesn't have to be injected into the DOM but it DOES have to exist in some capacity.
jQuery's live() isn't a magical mystery, it just uses event delegation, so it attaches the event to a parent element, such as the table and then decides what happens dependent on the target of the click. Here's a rudimentary example. I register a handler to the 'body' element, and then I test each time to see what the target is, if it's a TD element I doSomething() ->
document.body.onclick = function(e) {
var realTarget = e ? e.target : window.event.srcElement;
if ( realTarget.nodeName.toLowerCase() === 'td' ) {
doSomething();
}
};
Event delegation relies on something called event bubbling (or "propogation") which is the way in which modern browsers implement the event model. Each event, when triggered will travel upwards through the DOM until it can go no further. So if you click on an anchor within a paragraph the anchor's 'click' event will fire and THEN the paragraph's 'click' event will fire etc. etc.
jQuery 1.3+ has a new live() function that can set up event handlers for elements that don't exist yet .. check it out
You have to wait for the element to be added to the page, then add the event handler then.
There is no easy way to say "add this to all elements of this type, now and in the future".
It is possible to have a timer periodically check the page for new elements, applying a queue of events (or other properties) to them as they appear, all behind the scenes. This can be abstracted out and re-used, for example Jquery can do that sort of thing.
As JimmyP pointed out, your problem can easily be solved using event bubbling. You might consider writing a wrapper function to work around browser inconsistencies - my own version can be found here and would be used like this:
capture('click', '#element-id', function(event) {
// `this` will be the originating element
// return `false` to prevent default action
});