Handle Objects And The 'this' Keyword When Using Event Listeners?
Feb 24, 2009
So I know all about the caviats of the 'this' keyword when calling object functions from event listeners:
Code:
var foo = {bar: true, zoo: function() { return this.bar; }};
foo.zoo();
> true
a = foo.zoo;
a();
>
And I know that I can get around this by using an anonymous function so that 'this' is preserved in it's original context:
[Code]...
But then someone pointed out this article on memory leaks when using anonymous functions to call object methods because the anonymous function gets access to ALL variables in the enclosing environment and my not be properly disposed of by the garbage collector [URL] So that lead me to think about using a "3rd-person" approach to referencing object properties from within object methods.
[Code]...
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Sep 27, 2011
I feel like I must be missing something simple but I can't put my finger on it...
I'm moderately new to JS (programmed in other languages though) and am working on a Google Maps project.
This piece of code should show an alert of the region's name when a map polygon is clicked. Instead, no matter what polygon is clicked, it only does the name for the LAST iterated placemark. code...
What am I missing? What would be a better way of handling this?
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Aug 11, 2004
Here's the situation: I have a javascript object for controlling a custom DHTML scrollbar. So that I can use more than one on a page, the event listeners need to be passed a reference to the particular instance of the object that each needs to connect to, but as I discovered the hard way, inside an event listener, 'this' returns a reference to the DOM object throwing the event, rather than to the JS object. Short of coming up with a linked list of different objects and having the event handler search through it for the right object when an event is generated, then writing a reference to that object to some global variable, is there any convenient way to tie this together? I hope I've made myself clear enough...
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Jun 29, 2011
I am creating JS objects that have some properties that contain DOM nodes, and some of these DOM nodes have event listeners attached to them. When I delete such objects, do I first need to remove the event listeners attached to some of the DOM nodes? And do I need to use removeChild on the DOM nodes that are properties of the object? Or does JavaScript take care of all that?
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Dec 16, 2010
The DOM Level 3 specification has a section (1.2.2.2) that talks briefly about "groups" of event listeners. What does this mean? Is this similar to attaching event listeners with a namespace, as in jQuery: "event.my_namespace"?
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Nov 17, 2011
every time a window is opened in our software , I built a function to get the win32 handle address for each object inside this window ,by its string name (this is something that remains unchanged). now,after opening the window in real time , and running the function, I have some value like this for example: 0x00b206d8. my question is , how cand I use this handle value in order to do some actions on this object- for example insert a value and etc... I need the correct syntax in order to do so ,
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Jul 20, 2005
I'm trying to make use of XMLHTTP object, but I've come across a problem. It seems that there is no way to create dynamic array of such XMLHTTP objects (to make several requests) and handle them properly. I was trying to use such code:
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Sep 9, 2009
Does anyone know where I can find a complete list of DOM/DHTML event types documented?
I'm trying to learn more about advanced event handling in JavaScript and I'd like to find lists of event types that I can attach/add event listeners to. I've been searching around and I've found a few resources, but nothing that seems complete.code...
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Sep 28, 2009
I'm having problems removing the event listeners, they dont seem to be removed
(I am currently only checking for non-ie browsers) code...
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Oct 29, 2007
I have PHP file called file1.php with an empty <div></div> in the middle. I've added a 'load' event listener so that on page load, it calls an AJAX function that calls file2.php. file2.php creates a table and loads it into the <div></div> in file1.php.
file2.php has <a> tags in it's <th> columns and I wish to trap when a user clicks on the column heading. The old way was to use the onclick() method but I'd rather use event listeners.
Here's my problem. I am getting "obj has no properties" when trying to add those listeners. I *think* it is because the code in file2.php isn't part of the original DOM tree for file1.php. So how can I use event listeners instead of onlclick()? I know I can add top the DOM by creating elements and appending them but that adds to the HTML code and my code is already in place via the AJAX call. What to do...? DO I just use the old passe onclick() method?
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Dec 3, 2009
I'm trying to add event listeners to multiple elements of the same class. The DOM is something like this [code]...
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May 24, 2009
When catcheck1 is unchecked, I want catcheck9 to uncheck. Why does this not work?
<html><head>
<script type="text/javascript">
// Checkbox event listeners.
function checkboxs() {
document.mapform.catcheck9.checked = false;
}
</script></head><body>
<form action="" name="mapform" id="mapform">
<input type="checkbox" id="catcheck1" name="catcheck9" onclick="checkboxs()" checked />
<input type="checkbox" id="catcheck9" name="catcheck9" checked />
</form></body></html>
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Nov 13, 2011
My plan is to create a JavaScript class, with some functions and variables, and one of the functions is called when a user clicks on a certain element. However, I need to find out the ID of the element that was clicked (in the example, that of the <p>) for further processing. It looks basically like the following:
[Code]...
The result was very crazy, because console.log(this) gave me the node as result, and console.log($(this)) did the same only as jQuery node, but trying to find out the attribute via jQuery gave undefined as result. I haven't checked if this.id would work (should probably), but I'd prefer to keep the whole script in jQuery, if possible. I suspect it may be an overusage of the 'this' keyword, but if so, what's the proper way to do it?
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May 19, 2010
I would like to monitor the innerhtml change of a div, what is the best way to accomplish this since it does not have an onchange event.
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Mar 2, 2011
I have a checkbox inside a div. I need to handle both click eventindependently. When I click on the checkbox, thediv click event is triggered too. Does anyone knows how to manage this?
Here is my code. When clicking on the checkbox, I get 2 alert boxes instead of 1.
jQuery
$(document).ready(function(){
$('div').bind('click' , function(event){
alert('a');
});
$('input').bind('click' , function(event){
[Code]...
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Sep 3, 2009
How to handle "onMouseOver" event with keyboard. With JQuery, "onMouseOver" on a "plus symbol", small banner with some text content will be shown, it has been working with "Mouse(input device)", but same effect has been expecting from "keyborad" tab ordering on to that particular "plus symbol".
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Jul 27, 2011
I am generating a report on submit click.Due to size of data query execution takes some time to display result, in mean time if user press reload button on browser toolbar consequently same query request going to database and the performance become slow down. I am able to restrict user from clicking F5 and ctrl+R button but not reload button. I there any way to handle event on reload button? or can we disable reload button on submit?
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Jul 16, 2009
how to handle window close event in all aspects? i.e. when window is closed using close button alt+f4 and closing the window by right clicking on the task bar
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Nov 29, 2010
I have one requiremnt,i.e, How to handle the browser back button event, when User click on the Browser Back button, i need to redirecting the our custom page, i.e Error page.
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Aug 14, 2010
I'm new at jQuery and probably misunderstanding something fairly fundamental. I have a table that looks like this:
[Code]...
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Mar 1, 2010
how to handle a callback of an event, before it performs the default href function.
<code>
<a href = '<?php $url ?>' onclick = myFunction(); return true;>Click Here</a>
</code>
I want the onclick event to finish completing and then perform the default href function, which is denoted by the "return true". The javascript "myFunction()" opens a window in a pop-up and it has a submit button in it. I would like to wait till this page loads in the pop-up window and only after the user clicks on the close button, the default href function needs to be carried out. I cannot figure out on how to get the callback from this event.
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Jun 28, 2011
I'm trying to build an SVG-based galaxy map for a space game, it pulls the details from MySQL using PHP and seems to work fine with the following code:
<a xlink:href="index.php?locate=galaxy&sub=planet&x=$x&y=$y" target="_top">
<circle cx="$x" cy="$y" r="$starRadius" fill="rgb($fill)">
<title>$name</title>
[code]....
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Oct 24, 2009
On touchstart and touchmove event, the event object has touches and targetTouches properties (see http://bit.ly/Q6uOD), however the jQuery.Event doesn't seem to copy these properties. I tried adding them to $.event.props like this:
$.each(['touches', 'targetTouches'], function(){
if (!($.inArray($.event.props, this))) {
$.event.props.push(this);
}
});
But it doesn't seem to work. The event an event listener received via jQuery hasn't the targetTouches property even if it's accessible via event.originalEvent.targetTouches or window.event.targetTouches.
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Jun 2, 2010
I am trying to add onclick event handler to many objects but I can't understand why it doesn't work. To assign event handler I use traditional approach as described in [URL]Heres the code (extract.js):
Code JavaScript:
//the class
function extract(){
[code]....
I know that both select tags don't have options, but I generate them with JS because they hold sequential numbers and this part has no impact on the problem at hand.Both functions help select next or previous index in a given select tag for greater comfort
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Sep 14, 2009
I have 2 or more objects that onclick(), will call the same function. Right now I have the following:
....
$("#obj1").change( function() {
setupPage();
});
$("#obj2").change( function() {
[Code].....
I was wondering if there is a way to simplify or clean up the code, since they are all doing the same thing and responding to the same event. This is just for refactoring reasons because my code is getting too long/messy.
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Jun 2, 2010
I have this code
<script type="text/javascript">
jQuery(document).ready(function(){
$("select").click(function(){
alert($(this).attr('id'));
});
});
</script>
<FORM><select name="category" id="#link1">
<option value=1>1</option>
<option value=2>2</option>
</select></FORM>
<FORM><select name="category" id="#link2">
<option value=1>1</option>
<option value=2>2</option>
</select></FORM>
<FORM><select name="category" id="#link3">
<option value=1>1</option>
<option value=2>2</option>
</select></FORM>
When I click on any of the select fields, I always get 3 subsequent alerts, each with the id of the clicked select field. What I would like is to have only 1 alert with the clicked select id, whenever I click it.
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