How can I check whether a radio button is selected

Question

I have two radio buttons within an HTML form. A dialog box appears when one of the fields is null. How can I check whether a radio button is selected?

Answer 1

With jQuery, it'd be something like

if ($('input[name=gender]:checked').length > 0) {
    // do something here
}

Let me break that down into pieces to cover it more clearly. jQuery processes things from left to right.

input[name=gender]:checked

1. input limits it to input tags.
2. [name=gender] limits it to tags with the name gender within the previous group.
3. :checked limits it to checkboxes/radio buttons that are selected within the previous group.

If you want to avoid this altogether, mark one of the radio buttons as checked (checked="checked") in the HTML code, which would guarantee that one radio button is always selected.

Answer 2

If you want vanilla JavaScript, don't want to clutter your markup by adding IDs on each radio button, and only care about modern browsers, the following functional approach is a little more tasteful to me than a for loop:

<form id="myForm">
<label>Who will be left?
  <label><input type="radio" name="output" value="knight" />Kurgan</label>
  <label><input type="radio" name="output" value="highlander" checked />Connor</label>
</label>
</form>

<script>
function getSelectedRadioValue (formElement, radioName) {
    return ([].slice.call(formElement[radioName]).filter(function (radio) {
        return radio.checked;
    }).pop() || {}).value;
}

var formEl = document.getElementById('myForm');
alert(
   getSelectedRadioValue(formEl, 'output') // 'highlander'
)
</script>

If neither is checked, it will return undefined (though you could change the line above to return something else, e.g., to get false returned, you could change the relevant line above to: }).pop() || {value:false}).value;).

There is also the forward-looking polyfill approach since the RadioNodeList interface should make it easy to just use a value property on the list of form child radio elements (found in the above code as formElement[radioName]), but that has its own problems: How to polyfill RadioNodeList?

Answer 3

This would be valid for radio buttons sharing the same name, no JQuery needed.

var x = Array.prototype.filter.call(document.getElementsByName('checkThing'), function(x) { return x.checked })[0];

If we are talking about checkboxes and we want a list with the checkboxes checked sharing a name:

var x = Array.prototype.filter.call(document.getElementsByName('checkThing'), function(x) { return x.checked });

Answer 4

HTML Code

<input type="radio" name="offline_payment_method" value="Cheque" >
<input type="radio" name="offline_payment_method" value="Wire Transfer" >

Javascript Code:

var off_payment_method = document.getElementsByName('offline_payment_method');
var ischecked_method = false;
for ( var i = 0; i < off_payment_method.length; i++) {
    if(off_payment_method[i].checked) {
        ischecked_method = true;
        break;
    }
}
if(!ischecked_method)   { //payment method button is not checked
    alert("Please choose Offline Payment Method");
}

Answer 5

Let's pretend you have HTML like this

<input type="radio" name="gender" id="gender_Male" value="Male" />
<input type="radio" name="gender" id="gender_Female" value="Female" />

For client-side validation, here's some Javascript to check which one is selected:

if(document.getElementById('gender_Male').checked) {
  //Male radio button is checked
}else if(document.getElementById('gender_Female').checked) {
  //Female radio button is checked
}

The above could be made more efficient depending on the exact nature of your markup but that should be enough to get you started.

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If you're just looking to see if any radio button is selected anywhere on the page, PrototypeJS makes it very easy.

Here's a function that will return true if at least one radio button is selected somewhere on the page. Again, this might need to be tweaked depending on your specific HTML.

function atLeastOneRadio() {
    return ($('input[type=radio]:checked').size() > 0);
}

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For server-side validation (remember, you can't depend entirely on Javascript for validation!), it would depend on your language of choice, but you'd but checking the gender value of the request string.

Answer 6

if(document.querySelectorAll('input[type="radio"][name="name_of_radio"]:checked').length < 1)