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uncheckable radio buttons with html attribute 'checked'

I am using this simple script provided from a friendly lad in #javascript to uncheck radio buttons:
$('.feed').on('click', 'input[type=radio]', function() {
var myParent = $(this).closest('div');
var ref = $(this);
if( myParent.data('val') == $(this).val() ){
var ref = myParent.find('.none input');
ref.prop('checked',true);
}
myParent.data('val',ref.val() )
});
Everything works fine, see this fiddle, but when I add the attribute 'checked' to one radio button you will actually have to click twice before you can uncheck it, see this fiddle. This got me thinking, is setting 'checked' as an attribute actually equal to checking the radio button by hand? Or why am I failing this?

This has nothing to do with adding an an attribute vs clicking, it's the additional code, specifically this line:
if (myParent.data('val') == $(this).val() ){
which says, if you clicked this before, then turn it off.
However, you're not telling the code that you've already (virtually) "clicked" it.
You can do this by adding the initial value to the 'myParent', one way is to add it to the html:
<div data-val='1'>
Updated fiddle: https://jsfiddle.net/8jh2k8u8/4/
An alternative is to initialise the parent via code by finding the radio that is selected (:checked):
var startup = $(".feed input[type=radio]:checked").first();
if (startup.length) {
startup.closest("div").data("val", startup.val())
}
Updated fiddle: https://jsfiddle.net/8jh2k8u8/5/

JQuery: Check if any radio button is checked using radio button class name

I realize similar question had earlier been answered on stack overflow a few times. I checked all the questions and none were similar to mine.
I have a html form that has some radio buttons. In my validation I want to check if atleast one of the radio buttons are checked.
My approach so far:
All radio buttons have same class
All radio buttons have same name
I need to
check if atleast one of the radio button is selecetd
read the value of selected button.
My Javascript so far
function supportFormValidation(){
var isChecked = $('.radioButton').attr('checked')?true:false;
alert(isChecked);
return false;}
This always returns false. But when I try to read vale by individual IDs of each radio button it returns true. Is there any way I can check if a radio button is checked by using the class name.
JSFiddle: http://jsfiddle.net/evj9nch3/

Just use :checked.
var isChecked = !!($('.radioButton:checked').length);

In order to access the checked property you need to use the prop function (after 1.6 anyways). Because the value is either true or false, it's considered a property of the element not an attribute.
Nits answer is a better way of doing it, but look below for the reason why your implementation isn't working.
Take a look at this post for more info
Here is a link to the fiddle
function supportFormValidation() {
var isChecked = $('.radioButton').prop('checked') ? true : false;
alert(isChecked);
return false;
};
supportFormValidation();
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type='checkbox' class='radioButton' checked='true' />

You can use this. I checked this is working
$(".ClassName").prop("checked", true)

jQuery CheckAll Toggle Not Quite Working Correctly

Using:
function CheckToggle(which){
jQuery(which).each(function() {
jQuery(this).attr('checked', !jQuery(this).attr('checked'));
});
}
On first click, all checkboxes get checked, click it again, and they get unchecked.
Second click, no checkmarks show in the boxes, however, the checked="checked" attribute does appear in the element, and dissapears if clicking the checkall again.
How can I keep them showing the checkmark?

In this situation, .prop() would be used instead of .attr(). But honestly, it'd be even better to not use either:
this.checked = !this.checked;

Use prop instead of attr
function CheckToggle(which){
jQuery(which).each(function() {
jQuery(this).prop('checked', !jQuery(this).attr('checked'));
});
}

Element has `checked` attributes but isn't checked?

I am using ThreeDubMedia's drag and drop selection feature to check and uncheck a couple checkboxes. It will check and uncheck them once, but no more than that. What's more, when I look at the elements by using inspect, they start without the checked attribute, as they should; they gain it when selected, as they should; and they lose it when selected again, as they should. However, this is where it gets strange. If I select it a third time, it gains the checked attribute, but does not check! And if I select it a fourth time, nothing happens! I have no idea what's causing this.
http://i.snag.gy/AieOg.jpg

Currently, you are actually removing the attribute (using removeAttr()) instead of just turning it off (e.g. prop('checked', false)).
You should be using prop(). The following works:
if (this.checked) {
$(this).prop('checked', false);
} else {
$(this).prop('checked',true);
}
jsFiddle here.
Or better yet, as #Pointy mentioned:
.drop(function( ev, dd ){
this.checked = !this.checked;
});
jsFiddle here.

select all checkboxes command jquery, javascript

I'm trying to get all of my checkboxes to be checked when clicking a link
looks like this: select all
inputs in a loop: <input type="checkbox" name="delete[$i]" value="1" />
jquery code:
var checked_status = this.checked;
$("input[name=delete]").each(function() {
this.checked = checked_status;
});
Can someone help me get it to check all.. ?
When clicking at the select all link, nothing seems to happen.. (not even an error)

Try the following.
Updated. The handler is tied to an anchor therefore there will be no this.checked attribute available.
$("#select_all").click(function(){
$("input[name^=delete]").attr('checked', 'checked');
});

jQuery Tutorial: Select All Checkbox

You're going to want to use the [name^=delete] selector ("starts with"), since your checkboxes names aren't exactly "delete", they're "delete[X]' for some number X.