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How to remove all spaces when pasting using jQuery or JavaScript instantly?

When a user pastes some text into a field I want to be able to remove all spaces instantly.
<input type="text" class="white-space-is-dead" value="dor on" />
$('.white-space-is-dead').change(function() {
$(this).val($(this).val().replace(/\s/g,""));
});
http://jsfiddle.net/U3CRg/22/
This code from another example works. But doesn't update until a user clicks on something besides the textbox. I am using MVC with jQuery/JavaScript.

Switch the event change for input, which will trigger whenever something is inputted into the field, even if text is being pasted.
$('.white-space-is-dead').on('input', function() {
$(this).val($(this).val().replace(/\s/g,""));
});
Take a look at jQuery Events to understand better what options you have.
Edit: updated the answer based on OP's comment and what I found on this answer.

The regex wasnt doing what you wanted. This works but does not fire until the text input loses focus.
$('.white-space-is-dead').change(function() {
$(this).val($(this).val().replace(/ /g,''));
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" class="white-space-is-dead" value="dor on" />

Check a radio button with javascript

For some reason, I can't seem to figure this out.
I have some radio buttons in my html which toggles categories:
<input type="radio" name="main-categories" id="_1234" value="1234" /> // All
<input type="radio" name="main-categories" id="_2345" value="2345" /> // Certain category
<input type="radio" name="main-categories" id="_3456" value="3456" /> // Certain category
<input type="radio" name="main-categories" id="_4567" value="4567" /> // Certain category
The user can select whichever he/she wants, but when an certain event triggers, I want to set 1234 to be set checked radio button, because this is the default checked radio button.
I have tried versions of this (with and without jQuery):
document.getElementById('#_1234').checked = true;
But it doesn't seem to update. I need it to visibly update so the user can see it.
Can anybody help?
EDIT: I'm just tired and overlooked the #, thanks for pointing it out, that and $.prop().

Do not mix CSS/JQuery syntax (# for identifier) with native JS.
Native JS solution:
document.getElementById("_1234").checked = true;
JQuery solution:
$("#_1234").prop("checked", true);

If you want to set the "1234" button, you need to use its "id":
document.getElementById("_1234").checked = true;
When you're using the browser API ("getElementById"), you don't use selector syntax; you just pass the actual "id" value you're looking for. You use selector syntax with jQuery or .querySelector() and .querySelectorAll().

Today, in the year 2016, it is safe to use document.querySelector without knowing the ID (especially if you have more than 2 radio buttons):
document.querySelector("input[name=main-categories]:checked").value

Easiest way would probably be with jQuery, as follows:
$(document).ready(function(){
$("#_1234").attr("checked","checked");
})
This adds a new attribute "checked" (which in HTML does not need a value).
Just remember to include the jQuery library:
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>

By using document.getElementById() function you don't have to pass # before element's id.
Code:
document.getElementById('_1234').checked = true;
Demo:
JSFiddle

I was able to select (check) a radio input button by using this Javascript code in Firefox 72, within a Web Extension option page to LOAD the value:
var reloadItem = browser.storage.sync.get('reload_mode');
reloadItem.then((response) => {
if (response["reload_mode"] == "Periodic") {
document.querySelector('input[name=reload_mode][value="Periodic"]').click();
} else if (response["reload_mode"] == "Page Bottom") {
document.querySelector('input[name=reload_mode][value="Page Bottom"]').click();
} else {
document.querySelector('input[name=reload_mode][value="Both"]').click();
}
});
Where the associated code to SAVE the value was:
reload_mode: document.querySelector('input[name=reload_mode]:checked').value
Given HTML like the following:
<input type="radio" id="periodic" name="reload_mode" value="Periodic">
<label for="periodic">Periodic</label><br>
<input type="radio" id="bottom" name="reload_mode" value="Page Bottom">
<label for="bottom">Page Bottom</label><br>
<input type="radio" id="both" name="reload_mode" value="Both">
<label for="both">Both</label></br></br>

It seems the item.checked property of a HTML radio button cannot be changed with JavaScript in Internet Explorer, or in some older browsers.
I also tried setting the "checked" attribute, using:
item.setAttribute("checked", ""); I know the property can be set by default,
but I need just to change the checked attribute at runtime.
As a workarround, I found another method, which could be working. I had called the item.click(); method of a radio button. And the control has been selected. But the control must be already added to the HTML document, in order to receive the click event.

Using jQuery to check boxes based on user input (to another check box)

This is a very simple use of jQuery that I can't get working.
When one check box is checked, I'd like the other to become checked.
HTML:
<input onchange="toggleRegion()" id="ESARO" type="checkbox" class="region"
value="ESARO" name="ESARO">ESARO
<br /><br />
<input type="checkbox" class="country" value="Afghanistan" name="country2"
/>Afghanistan
jQuery:
function toggleRegion() {
if ($('#ESARO').is(':checked')) {
$('input[value="Afghanistan"]').attr('checked', true);
}
}
jsfiddle:
http://jsfiddle.net/jsJU8/
What I've tried:
I have another function which does a very similar thing for a group of check boxes by class which works perfectly:
function toggleStatus() {
if ($('#TLO1').is(':checked')) {
$('.country').attr('checked', true);
}
}
So I presume that the error lies in the selection of the element by value, rather than by class, as this is the only difference between the functions.
To this end I've tried adjusting that selector;'s syntax to match various examples I've found (single quote, double quote, no quote etc) but haven't had any luck.#
Although I note that it may be a possible error that I'm using javascript (onChange) to call a jQuery function. Is that an issue?
All help greatly appreciated - thank you

You code is working but you have to choose no-wrap (body) option in first drop down.
Live Demo
function toggleRegion() {
if ($('#ESARO').is(':checked')) {
$('input[value="Afghanistan"]').attr('checked', true);
}
}

Prevent checkbox from ticking/checking COMPLETELY

I have been asked to disable the "ticking" of a checkbox. I am not being asked to disable the checkbox, but to simply disable the "ticking".
In other words, a user will think that a checkbox is tickable, but it is not. Instead, clicking on the checkbox will cause a modal dialog to appear, giving the user more options to turn on or off the feature that the checkbox represents. If the options chosen in the dialog cause the feature to be turned on, then the checkbox will be ticked.
Now, the real problem is that for a split second, you can still see that the checkbox is being ticked.
I have tried an approach like this:
<input type='checkbox' onclick='return false' onkeydown='return false' />
$('input[type="checkbox"]').click(function(event) {
event.preventDefault();
alert('Break');
});
If you run this, the alert will appear, showing that the tick is visible (the alert is just there to demonstrate that it still does get ticked, in production, the alert is not there). On some users with slower machines and/or in browsers with slow renderers/javascript, users can see a very faint flicker (the flicker sometimes lasts for half a second, which is noticeable).
A tester in my team has flagged this as a defect and I am supposed to fix it. I'm not sure what else I can try to prevent the tick in the checkbox from flickering!

From my point of view it is as simple as:
$(this).prop('checked', !$(this).prop('checked'));
Works both for checked and unchecked boxes

Try
event.stopPropagation();
http://jsfiddle.net/DrKfE/3/

Best solution I've come up with:
$('input[type="checkbox"]').click(function(event) {
var $checkbox = $(this);
// Ensures this code runs AFTER the browser handles click however it wants.
setTimeout(function() {
$checkbox.removeAttr('checked');
}, 0);
event.preventDefault();
event.stopPropagation();
});

This effect can't be suppressed I fear. As soon as you click on the checkbox, the state (and rendering) is changed. Then the event handlers will be called. If you do a event.preventDefault(), the checkbox will be reset after all the handlers are executed. If your handler has a long execution time (easily testable with a modal alert()) and/or the rendering engine repaints before reseting, the box will flicker.
$('input[type="checkbox"]').click(function(event) {
this.checked = false; // reset first
event.preventDefault();
// event.stopPropagation() like in Zoltan's answer would also spare some
// handler execution time, but is no more needed here
// then do the heavy processing:
alert('Break');
});
This solution will reduce the flickering to a minimum, but can't hinder it really. See Thr4wn's and RobG's answer for how to simulate a checkbox. I would prefer the following:
<button id="settings" title="open extended settings">
<img src="default_checkbox.png" />
</button>
document.getElementById("settings").addEventListener("click", function(e) {
var img = this.getElementsByTagName("img")[0]);
openExtendedSettingsDialog(function callbackTick() {
img.src = "checked_checkbox.png";
}, function callbackUntick() {
img.src = "unchecked_checkbox.png";
});
}, false);

It is very important to use return false at the end.
Something like this:
$("#checkbox").click((e) => {
e.stopPropagation();
return false;
});

Isn't is simpler ? :
<input type="checkbox" onchange="this.checked = !this.checked">

TL:DR;
HTML api's execute before JavaScript. So you must use JavaScript to undo HTML's changes.
event.target.checked = false
WHAT is the problem?
Strictly speaking: we cannot "stop" the checkbox from being ticked. Why not? Because "being ticked" exactly means that the DOM's, HTML <input> element has a checked property value of true or false, which is immediately assigned by the HTML api
console.log(event.target.checked) // will be opposite of the previous value
So it's worth explicitly mentioning this HTML api is called before scripts. Which is intuitive and should make sense, because all JavaScript files are themselves the assignment of a <script> element's attribute src, and the ancestral relationship in the DOM tree, between your <input> in question, and the <script> element running your JavaScript, is extremely important to consider.
HOW to get our solution
The HTML assigned value has not yet been painted before we have a chance to intercept the control flow (via JS file like jQuery), so we simply re-assign the checked property to a boolean value we want: false (in your case).
So in conclusion, we CAN, in-effect, "stop" the checkbox from being checked, by simply ensuring that the checked property is false on the next render and thus, won't see any changes.

Why not simply add a class in your CSS that sets pointer-events: none;?
Something like:
<style>
input.lockedCbx { pointer-events: none; }
</style>
...
<input type="checkbox" class="lockedCbx" tabindex=-1 />
...
You need the tabindex=-1 to prevent users from tabbing into the checkbox and pressing a space bar to toggle.
Now in theory you could avoid the class and use the tabindex=-1 to control the disabling as in:
<script>
input[type="checkbox"][tabindex="-1"] { pointer-events: none; }
</script>

With CSS, you can change the image of the checkbox. See http://ryanfait.com/resources/custom-checkboxes-and-radio-buttons/ and also CSS Styling Checkboxes .
I would disable the checkbox, but replace it with an image of a working checkbox. That way the checkbox doesn't look disabled, but won't be clickable.

Wrap the checkbox with another element that somehow blocks pointer events (probably via CSS). Then, handle the wrapper's click event instead of the checkbox directly. This can be done a number of ways but here's a relatively simple example implementation:
$('input[type="checkbox"').parent('.disabled').click( function() {
// Add in whatever functionality you need here
alert('Break');
});
/* Insert an invisible element that covers the checkbox */
.disabled {
position: relative;
}
.disabled::after {
content: "";
position: absolute;
top: 0px;
left: 0px;
right: 0px;
bottom: 0px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<!-- Only wrapped checkboxes are "disabled" -->
<input type="checkbox" />
<span class="disabled"><input type="checkbox" /></span>
<input type="checkbox" />
<span class="disabled"><input type="checkbox" /></span>
<span class="disabled"><input type="checkbox" /></span>
<input type="checkbox" />
Note: You could also add the wrapper elements programmatically, if you would like.

Sounds to me like you are using the wrong interface element, a more suitable one would be a button that is disabled by default, but enabled when that option is available. The image displayed can be whatever you want.
<button disabled onclick="doSomething();">Some option</button>
When users have selected that feature, enable the button. The image on the button can be modified by CSS depending on whether it's enabled or not, or by the enable/disable function.
e.g.
<script type="text/javascript">
function setOption(el) {
var idMap = {option1:'b0', option2: 'b1'};
document.getElementById(idMap[el.value]).disabled = !el.checked;
}
</script>
<div><p>Select options</p>
<input type="checkbox" onclick="setOption(this);" value="option1"> Option 1
<br>
<input type="checkbox" onclick="setOption(this);" value="option2"> Option 2
<br>
</div>
<div>
<button id="b0" onclick="alert('Select…');" disabled>Option 1 settings</button>
<button id="b1" onclick="alert('Select…');" disabled>Option 2 settings</button>
</div>

The Event.preventDefault method should work for change, keydown, and mousedown events, but doesn't in my testing.
My solution to this problem in a Mozilla Firefox 53.0 extension was to toggle an HTML class that enabled/disabled the CSS declaration pointer-events: none being applied to the checkbox. This addresses the cursor-based case, but not the key-based case. See https://www.w3.org/TR/SVG2/interact.html#PointerEventsProp.
I addressed the key-based case by adding/removing an HTML tabindex="-1" attribute. See https://html.spec.whatwg.org/multipage/interaction.html#attr-tabindex.
Note that disabling pointer-events will disable your ability to trigger CSS cursors on hover (e.g., cursor: not-allowed). My checkbox was already wrapped in a span element, so I added an HTML class to that span element which I then retargeted my CSS cursor declaration onto.
Also note that adding a tabindex="-1" attribute will not remove focus from the checkbox, so one will need to explicitly defocus it by using the HTMLElement.blur() method or by focusing another element to prevent key-based input if the checkbox is the active element at the time the attribute is added. Whether or not the checkbox is the focused element can be tested with my_checkbox.isEqualNode(document.activeElement).

Simply revert the value back
$('input[type="checkbox"]').on('change', function(e) {
if (new Date().getDate() === 13) {
$(this).prop('checked', !$(this).prop('checked'));
e.preventDefault();
return false;
}
// some code here
});

Add this to click event in js file
event.stopPropagation();

$('#term-input').on('change click',function (e){
e.preventDefault();
})
works for me

jQuery and If statement to de-select radio buttons

Well, I'm stuck and have been banging my head for a little while now to try to figure what I'm doing wrong.
Scenario:
I have a question with a Yes/No answer (ie 2 radio buttons). When a user selects the either Yes or No, I call a function to .toggle() a hidden div to show a link. That works great. And if they go back and check that Yes/No again it disappears again due to the .toggle()
My issue is that if a user clicks the No (and the link is shown) but then clicks the Yes I want the link that is showing due to the No result to disappear and vice-versa.
So basically only show 1 link at a time.
I figured that maybe an If statement would work but I can't seem to get it right.
My code:
<div id="Question1">
<div>Do you kazoo?</div>
<input type="radio" ID="Q1RB1" runat="server" value="Yes" text="Yes" name="RadioGroup1"/>Yes<br />
<input type="radio" ID="Q1RB2" runat="server" value="No" text="No" name="RadioGroup1"/> No
<span id="Q1RB1Results" style="display:none"> <a href=#>Click here</a></span>
<span id="Q1RB2Results" style="display:none"> <a href=#>Click here</a></span>
</div>
My jQuery code that works for each individual radio button:
$("input[id$=Q1RB1]:radio").change(function () {
$("[id$=Q1RB1Results]").toggle();
});
$("input[id$=Q1RB2]:radio").change(function () {
$("[id$=Q1RB2Results]").toggle();
});
This is the If statement I'm trying to get to work. Amy I going about this the wrong way?
if ($("input[id$=Q1RB2]").is(":checked")) {
$("input[id$=Q1RB2]:radio").change(function () {
$("[id$=Q1RB2Results]").toggle();
});
});
Thanks for any thoughts/advice. I've tried a multitude of answers here in Stackoverflow and the 'net but can't seem to figure out what I'm doing wrong. :(
~V
Update: I put a sample form and the dialogue up on JSFiddle. http://jsfiddle.net/Valien/7uN6z/4/ I tried some of the solutions mentioned here and couldn't get them working so not sure what I'm doing wrong.

When you register an event listener in JQuery (.change, .click, .blur, etc.), the Javascript engine matches the selector and applies them at that point. With that in mind, you can rearrange your code (which is close to being right) to this, which should do the trick:
/* The function you're about to define applies to all radio button
inputs whose ID ends with Q1RB2 */
$("input[id$=Q1RB2]:radio").change(function()
{
/* Inside the change function, $(this) refers to the instance that
was changed. So, this checks to see if the instance that was just
changed is currently checked, after being changed. */
if ($(this).is(":checked"))
{
// If that was the case, then toggle the item
$("[id$=Q1RB2Results]").toggle();
}
});

Try this:
$('input:radio[name=RadioGroup1]').change(function(){
var show = "#" + $(this).attr('id') + 'Results';
$('#Question1 span').hide();
$(show).show();
});

I believe this is what you need:
// declare common variables so it's easier to target
var question = $("#Question1"),
group = question.find("input[name='RadioGroup1']"),
span = question.find("span");
// change listener for each radio button group
group.click(function(){
var id = $(this).attr("id"); // get the radio button id for reference
span.each(function(){ // loop through each span and check which one to hide/show
var item = $(this);
if (item.attr("id")===id+"Results") { item.show(); } else { item.hide(); }
});
});