check/uncheck radio input with javascript

jQuery edition

// bind to retrieve old status
$('input[type="radio"]').mousedown(function() { 
    // if it was checked before
    if(this.checked) {
        // bind event to reset state after click is completed
        $(this).mouseup(function() {  
            // bind param, because "this" will point somewhere else in setTimeout
            var radio = this;
            // apparently if you do it immediatelly, it will be overriden, hence wait a tiny bit
            setTimeout(function() { 
                radio.checked = false; 
            }, 5); 
            // don't handle mouseup anymore unless bound again
            $(this).unbind('mouseup');
        });
    }
});

But again, this is not how radio buttons are intended to be used. I think you'd be better of with a set checkbox'es where you could uncheck all other checkboxes than the current clicked (hence always max 1 selected)

A working example

I use this. You simply store the pre-click value and ! it into the value.

<input type=radio name="myoptions" value="1" 
   onmousedown="this.tag = this.checked;" onclick="this.checked = !this.tag;">

It's quite simple, just follow the simple example:

var rdblength = document.formname.elementname.length;
alert('length=' + rdblength);
for(i=0; i < rdblength; i++) {
    document.formname.elementname[i].checked = false;
}

Just find the length and make every index checked=true/false

Ping me at: http://manojbardhan2009.blogspot.com

This behavior is not the expected one for radio buttons and I don't recommend it at all. Try to find another way of achieving this. Use another widget or another option to reset the field value:

http://jsfiddle.net/marcosfromero/rRTE8/

try this:

function resetMeIfChecked(radio){           
    if(radio.checked && radio.value == window.lastrv){
        $(radio).removeAttr('checked');
        window.lastrv = 0;
    }
    else
        window.lastrv = radio.value;
}

<input value="1" name="options" checked="checked" type="radio" onClick="resetMeIfChecked(this)" />A
<input value="2" name="options" type="radio" onClick="resetMeIfChecked(this)" />B
<input value="3" name="options" type="radio" onClick="resetMeIfChecked(this)" />C

I had the same problem and figured it out. None of the answers above work exactly as I wanted - most of them require an additional button to reset the radio. The goal was to uncheck radio by clicking on the radio itself.

Here's the fiddle: http://jsfiddle.net/MEk5Q/1/

The problem was very complicated because the radio button value changes BEFORE the click event fires so when we're listening to the event we can't tell if the radio button was already checked or not. In both cases it is already checked. Another approach was to listen to mousedown event. Unlike click, it fires before changing radio checked attribute but unchecking it inside event handler gives us nothing since it is checked back again during mouseup event.

My answer is a little ugly workaround so I generally don't suggest it to others and I'll probably abandon it myself. It works but it involves 20ms timeout function which I'm not fond of in cases like this.

Here is the code explanation:

$('input[type="radio"]').on('mousedown', function() {
    if (this.checked) { //on mousedown we can easily determine if the radio is already checked
        this.dataset.check = '1'; //if so, we set a custom attribute (in DOM it would be data-check="1")
    }
}).on('mouseup', function() {
    if (this.dataset.check) { //then on mouseup we determine if the radio was just meant to be unchecked
        var radio = this;
        setTimeout(function() {radio.checked = false;}, 20); //we give it a 20ms delay because radio checking fires right after mouseup event
        delete this.dataset.check; //get rid of our custom attribute
    }
});

As a timeout function I could use a string (less writing) but as far as I know it would be eval'ed. Though I don't trust eval function, I prefered anonymous function.

One more thing - one could ask why spreading the code into two separate event handlers while we can fire the timeout function on mousedown? Well, what if someone press the mouse on a radio and holds it for a few secs or even someone is simply a very slow person ;). Generally, with this solution we omit the problem of lag between mousedown and mouseup.

If you need some more info about dataset, here's the MDN reference: https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement.dataset This property came with HTML5 and might be not cross-browser, I guess, so if you want 100% compatibility, replace it with any other solution that'll contain the data, you name it.

Sorry about jQuery here and there but I hope you're fine with it - it was much easier that way.

Hope you'll enjoy it.

I was never too happy about being forced to aim at that tiny radio button, so I came up with a larger target AND a way to turn a radio group off without resorting to anything that would upset the HTML / JavaScript purists.

The technique relies on not molesting the radio buttons at all via event handlers, but checking for a readonly proxy for each one instead. Everything is contained in what's below in pure JavaScript using a radio group to select a type of cheese, or no cheese at all.

I purposely used no styling in this example to avoid that added layer. The dump button will tell you what the three checked states are, so use it to interrogate what happened after hitting the radio or text input elements. For example simplicity I used a global to remember the former state, but a more elegant method is to use a dataset, which I what I use in the real code of my application.

<!DOCTYPE html>
<html>
<head>
  <title>Uncheck a radio button</title>
<script>
function attachEventListener(target, eventType, functionRef, capture) {
   "use strict";
   if (typeof target.addEventListener !== 'undefined') {
      // Most modern browsers
      target.addEventListener(eventType, functionRef, capture);
   } else if (typeof target.attachEvent !== 'undefined') {
      // IE
      target.attachEvent('on' + eventType, functionRef);
   } else {
      eventType = 'on' + eventType;
      if (typeof target[eventType] === 'function') {
         var oldListener = target[eventType];
         target[eventType] = function() {
            oldListener();
            return functionRef();
         };
      } else {
         target[eventType] = functionRef;
      }
   }
}
</script>
</head>

<body>
<form>
<input id="Cheddar-radio"  class="radio" type="radio" name="Cheeses-0" value="Cheddar Cheese"  tabindex="-1"></input>
<input id="Cheddar-text"                 type="text"  readonly         value="Cheddar Cheese"      tabindex="-1"></input><br>
<input id="Swiss-radio"    class="radio" type="radio" name="Cheeses-0" value="Swiss Cheese"    tabindex="-1"></input>
<input id="Swiss-text"                   type="text"  readonly         value="Swiss Cheese"    tabindex="-1"></input><br>
<input id="American-radio" class="radio" type="radio" name="Cheeses-0" value="American Cheese" tabindex="-1"></input>
<input id="American-text"                type="text"  readonly         value="American Cheese" tabindex="-1"></input><br><br>

<input onclick="dumpStates()" type="button" name="button" value="dump" tabindex="-1"></input>

</form>
<script>
window.onload = addRadioListeners;

function addRadioListeners() { // But do it on the -text elements.
   attachEventListener(document.getElementById('Cheddar-text') , 'mousedown', rememberCurrentState, false);
   attachEventListener(document.getElementById('Swiss-text')   , 'mousedown', rememberCurrentState, false);
   attachEventListener(document.getElementById('American-text'), 'mousedown', rememberCurrentState, false);

   attachEventListener(document.getElementById('Cheddar-text') , 'mouseup', checkNewState, false);
   attachEventListener(document.getElementById('Swiss-text')   , 'mouseup', checkNewState, false);
   attachEventListener(document.getElementById('American-text'), 'mouseup', checkNewState, false);
}

function dumpStates() {
   console.log(document.getElementById('Cheddar-radio').checked +
               ' ' + document.getElementById('Swiss-radio').checked +
               ' ' + document.getElementById('American-radio').checked);
}

var elementWasChecked; // Global - Could just as well use a dataset attribute
                       // on either the -radio or -text element and check it instead.

function rememberCurrentState(event) {
   var element;
   var radioElement;

   element = event.target;

   radioElement = document.getElementById(element.id.replace(/text/,'radio'));
   elementWasChecked = radioElement.checked;

   radioElement.checked = true;

}

function checkNewState(event) {
   var element;
   var radioElement;

   element = event.target;
   radioElement = document.getElementById(element.id.replace(/text/,'radio'));

   var currentState = radioElement.checked;

   if (elementWasChecked === true && currentState === true) {
      console.log('Changing ' + radioElement.id + ' to false.');
      radioElement.checked = false;
   }
};

</script>
</body>
</html>

If you click on the radio buttons they work as expected. If you click on the text items next to each, they are a proxy for the radio buttons with one exception. If you click on a text item that has an associated radio button that's already checked, it will uncheck it. Therefore, the text proxy's are event triggered, and not the radio buttons.

The added benefit is that you can now hit the larger text target too.

If you want to make it simple and wouldn't mind using a double-click event try something like this:

<input name="options" type="radio" ondblclick="this.checked=false;">

@jerjer's answer is almost perfect, but radios can be switched also by arrows if the radio group has the focus (so mousedown event is not enough). Alas, the radio group also gets checked when activated by focus shift (Tab), which can undesirably check one option. Therefore space should uncheck the focused radio, just like the checkbox behavior.

This code fixes that for all radios (Most credit still goes to jerjer):

window.addEventListener("DOMContentLoaded", function() {
  var radios = document.querySelectorAll("input[type=radio]");
  for(var i=0; i<radios.length; ++i) {
    radios[i].addEventListener("click", function(e) {
      if(e.target.checked && e.target.value == window.lastrv){
        e.target.checked = false;
        window.lastrv = 0;
      }
      else
        window.lastrv = e.target.value;
    });

    radios[i].addEventListener("keypress", function(e) {
      if(e.keyCode==32) e.target.click();
    });
  }
});