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When checkbox is clicked, how to know the state of the checkboxes

EDIT:
Please read the end part of the post, I know the part that tells which are unchecked needs to be inside the block of code, the issue here is that the first part of the code is not registering the "click". So can't do anything without that.
E2: May take the suggestion of adding a onclick to the boxes, since the code for boxes is generated with JS, I would add it once and all of them will get the function call, but that feels kinda ugly
I have a set of check boxes, and when one is clicked I need to return the values of the unchecked ones.
HTML:
<div id="myCheckboxList">
<input type="checkbox" name="myList" value="1" checked>1
<input type="checkbox" name="myList" value="2" checked>2
<input type="checkbox" name="myList" value="3" checked>3
</div>
JavaScript:
$(function(){
$("input[name=myList]").on("click",function(){
console.log("triggered");
//code here to find which ones are unchecked
});
});
I have tried to also add this in the code
$boxes = $('input[name=myList]:not(:checked)');
$boxes.each(function(){
// Do stuff with for each unchecked box
});
Unfortunatly the "triggered" in not getting output to console, so unsure why it is so, and how would i get an event to happen when the checkboxes are hit

I copied your code directly to a fiddle, and it works fine. You could be missing the jquery library?
EDIT:
Just to be sure, I updated the snippet to generate the inputs, and it still works fine.
$(function() {
var html = '<input type="checkbox" name="myList" value="1" checked>1'
+'<input type="checkbox" name="myList" value="2" checked>2'
+'<input type="checkbox" name="myList" value="3" checked>3';
$("#myCheckboxList").html(html);
$("input[name=myList]").on("click", function() {
console.log("triggered");
//code here to find which ones are unchecked
$boxes = $('input[name=myList]:not(:checked)');
$boxes.each(function() {
console.log($(this).val());
});
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="myCheckboxList">
</div>

Easiest way would be to:
let v = $(this).attr('value');
if(v === 1){ // box 1 selected
Adding this inside your 'click' handler should work.

You need to add your each script inside your click event.
$(function(){
$("input[name=myList]").on("click",function(){
$("input[name=myList]:not(:checked)").each(function() {
console.log($(this).val());
});
});
});
<div id="myCheckboxList">
<input type="checkbox" name="myList" value="1" checked>1
<input type="checkbox" name="myList" value="2" checked>2
<input type="checkbox" name="myList" value="3" checked>3
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

Another solution is to add an "onclick" method in your html. This will call a javascript function whenever the checkbox is clicked. That function can contain any logic for your checkboxes.
<input type="checkbox" name="myList" value="1" checked onclick="checkboxChangeEvent();">1
Then you can implement your javascript function to return a list of unchecked boxes or find the input boxes by name and return the alert as in previous answers.
function checkboxChangeEvent(){
$boxes = $('input[name=myList]:not(:checked)');
$boxes.each(function() {
alert($(this).val());
});
}

Try like this:
$(function(){
$("input[name=myList]").on("click",function(){
var uncheck=[];
//console.log("triggered");
//code here to find which ones are unchecked
$boxes = $("input[name=myList]:not(:checked)");
$boxes.each(function(){
// Do stuff with for each unchecked box
uncheck.push($(this).attr('value'))
console.log(uncheck);
});
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="myCheckboxList">
<input type="checkbox" name="myList" value="1" checked>1
<input type="checkbox" name="myList" value="2" checked>2
<input type="checkbox" name="myList" value="3" checked>3
</div>

Cannot deselect radio button?

I have been attempting to allow radio buttons to be deselected using jQuery, but I am running into issues with the prop function. When this code runs, my conditional ($(e.currentTarget).prop('checked')) always evaluates to true.
Here is a fiddle which demonstrates my issue: Jsfiddle
FYI: I am using jQuery 1.8.2, and I cannot update it because it is a legacy project with many dependencies. Also, I MUST use radio buttons per the client's request.
Javascript:
$("input[name=optionMedia]").click(function(e) {
if ($(e.currentTarget).prop('checked')) {
$(e.currentTarget).prop('checked', false);
}
});
Html:
<input class="bigSizeInput" type="radio" id="audioVideo" name="optionMedia" value="1"/>
<input class="bigSizeInput" type="radio" id="showReel" name="optionMedia" value="2" />

You can do it like this
$('input.bigSizeInput').mouseup(function() {
if ($(this).is(':checked')) {
setTimeout(function() {
$('input.bigSizeInput:checked').prop('checked', false);
}, 1)
}
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input class="bigSizeInput" type="radio" id="audioVideo" name="optionMedia" value="1" />
<input class="bigSizeInput" type="radio" id="showReel" name="optionMedia" value="2" />

This is because checked is a property. If its there it is true, if its not it is not true. Hence you either should switch to a checkbox or use
$("..").removeProp('checked')

Using checkbox to check/uncheck is better than radio button. But if you want to use radio button, you need to check if radio is checked, copy it using and remove checked attribute of copied element and then insert it after target radio. At the end remove original radio.
$(document).on("mousedown", "input[name=optionMedia]", function(e) {
if (this.checked)
$(this).clone().prop('checked', false).insertAfter(this).end().remove();
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>
<input class="bigSizeInput" type="radio" id="audioVideo" name="optionMedia" value="1"/>
<input class="bigSizeInput" type="radio" id="showReel" name="optionMedia" value="2" />

Checkbox to toggle all selection

I have this javascript code
// Listen for click on toggle checkbox
$('#select-all').click(function(event) {
if(this.checked) {
// Iterate each checkbox
$(':checkbox').each(function() {
this.checked = true;
});
}
});
And I have this
<form action="" method="POST">
Toggle All :
<input type="checkbox" name="select-all" id="select-all" />
then at my table I have multiple checkbox
<input type="checkbox" name="checkbox-1" id="checkbox-1" value="1"> Select
<input type="checkbox" name="checkbox-2" id="checkbox-2" value="2"> Select
<input type="checkbox" name="checkbox-3" id="checkbox-3" value="3"> Select
<input type="checkbox" name="checkbox-4" id="checkbox-4" value="4"> Select
When I click on toggle all, it does not check checkbox-1 to checkbox-4
What went wrong in my javascript code.
Thanks!! I want to actually do a function that will send all the value of checkbox1-4 by post when they are checked on form submit.

Simply do like this.
$('#select-all').click(function(event) {
$(':checkbox').prop("checked", this.checked);
});
You do not need to loop through each checkbox to check all.
Demo
Wrap the code in dom ready if your script is in head tag
$(document).ready(function() {
$('#select-all').click(function(event) {
$(':checkbox').prop("checked", this.checked);
});
});

jQuery get the "event invoking" element

My problem is that when the checkbox below is clicked - the check function is called to check/uncheck all the checkboxes. But they have to change relatively to the invoking checkbox (the one with the "onchange" event).
The checkbox HTML declaration:
<input type="checkbox" onchange="$('input[type=checkbox][rel=users]').check();">
Sample JavaScript Code:
$.fn.check = function() {
$(this).each(function(){
$(this).attr('checked', checked);
});
}
And my question is: How can I get the DOM object corresponding to the "check all" checkbox?

Edit: Pass the this object of the checkAll to the function.
DEMO
<input type="checkbox"
onchange="$('input[type=checkbox][rel=users]').check(this);" />
Note the this is passed as .check(this)
And in the JS:
$(document).ready(function() {
$.fn.check = function(orgEl) {
$(this).each(function() {
$(this).attr('checked', orgEl.checked);
});
}
});
Old Post -
Bind the checkAll checkbox to an handler and call the fxn from inside.. See below,
HTML
<input type="checkbox" id="checkAll" >
JS
$(document).ready (function () {
$('#checkAll').click (function () {
//this inside is checkAll checkbox object.
$('input[type=checkbox][rel=users]').check();
});
});

Since you're binding this to the "checkall" checkbox, you have access to itself inline. So you can pass it to the jQuery .check() function you made and use it there. Look at this:
(please excuse my changes to your selecting, you can obviously use what you had before...but I would suggest using :checkbox instead of input[type=checkbox])
<html>
<head>
<script type="text/javascript" src="jquery-min.js"></script>
<script type="text/javascript">
$.fn.check = function (obj) {
$(this).each(function (){
this.checked = obj.checked;
});
}
</script>
</head>
<body>
<input type="checkbox" id="checkall" onclick="$('.check-item').check(this);" /><br />
<input type="checkbox" class="check-item" /><br />
<input type="checkbox" class="check-item" /><br />
<input type="checkbox" class="check-item" /><br />
<input type="checkbox" class="check-item" /><br />
<input type="checkbox" class="check-item" /><br />
<body>

View on JSFIDDLE.
I'm a fan of using HTML5 data attributes for stuff like this. With the following DOM structure, you can define your target checkboxes with a data-target attribute on the triggering checkbox. The target should be a valid jQuery selector string.
HTML:
<input type="checkbox" id="checkUsers" class="checkAll" data-target="input[type=checkbox][rel=users]">
<label for="checkUsers">Users:</label>
<input type="checkbox" rel="users">
<input type="checkbox" rel="users">
<input type="checkbox" rel="users">
<input type="checkbox" rel="users">
<input type="checkbox" rel="users">
<br><br>
<input type="checkbox" id="checkPlaces" class="checkAll" data-target="input[type=checkbox][rel=places]">
<label for="checkPlaces">Places:</label>
<input type="checkbox" rel="places">
<input type="checkbox" rel="places">
<input type="checkbox" rel="places">
<input type="checkbox" rel="places">
<input type="checkbox" rel="places">
Then you setup the plugin to use the target you defined to trigger the checks/unchecks based on the triggering checkbox's checked attribute.
Plugin:
(function( $ ){
$.fn.check = function() {
// "this" is a jQuery object of the checkbox that was clicked.
var target = this.data("target");
$(target).attr("checked", this[0].checked);
return this; //maintain chainability
};
})( jQuery );
The real benefit of this method is that it allows you to only have to manage one event handler declaration by attaching the event to a class instead of an id.
Event Handler Declaration:
$(function(){
$(".checkAll").click(function(){
$(this).check();
});
});

How to replace a p tag value if a radio is checked?

I want replace a p tag value if a radio is checked.
I write some JS to do this,but nothing changed.
this is my code(I use jquery)
<script>
$(function(){
if ($('#A:checked')) {
$("#change_me").html('<input type="radio" value="1" name="fruit">')
}
if ($('#B:checked')) {
$("#change_me").html('<input type="radio" value="2" name="fruit">')
}
}
</script>
<input type="radio" name="e" id="A" checked="checked">
<input type="radio" name="e" id="B">
<p id="change_me">
<input type="radio" value="1" name="fruit">
</p>
Thanks.

The :checked selector matches elements that are currently checked.
Writing $('#B:checked') returns a jQuery object containing either zero or one element. It cannot be used directly as a condition.
Instead, you can check if ($('#B:checked').length) to see whether the jQuery object has anything in it.

First, you don't need to recreate the radio button if only the value is changing.
$(function(){
if ($('#A:checked').size() > 0) {
$("#change_me input[type=radio]").val('1')
}
if ($('#B:checked').size() > 0) {
$("#change_me input[type=radio]").val('2')
}
}
HTML:
<input type="radio" name="e" id="A" checked="checked">
<input type="radio" name="e" id="B">
<p id="change_me">
<input type="radio" value="1" name="fruit">
</p>

Replace the JavaScript code you have with the following
$(function(){
$('input[name=e]').change(function(){
if($(this).attr('id') == 'A')
{
$("#change_me input").val('1');
}
else
{
$("#change_me input").val('2');
}
});
});