How to get the value of selected radio button using jQuery

Just use below code and modified according to your need.

Note: this is very useful for COD and Prepaid charge addition using javascript, jquery, PHP

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>


<br><br><br>
<script>
    $(document).ready(function(){
        $("input[type='radio']").change(function(){
         var radioValue = $("input[name='payment_method']:checked").val();
            if(radioValue){
                alert("Your are a - " + radioValue);


                 var totl     = parseInt($("#total_amount").val());

          var shipping_value = totl ;
            
            // alert(pay_method);
            // console.log(pay_method);

            if(radioValue !=0)
                 {
                      $("#pay").hide();

                   let cod_charge = 50;

                   var totl = totl + cod_charge;


                     $("#gttotal").html("<label>Total Amount</label> <input type='text' name='total_amount' value='"+totl+"' readonly>");
                 }

                 

                 else
                 {
                   $("#gttotal").html("<label>Total Amount</label> <input type='text' name='total_amount' value='"+totl+"' readonly>");
                 }




            }
        });
    });
</script>

<form action="forms.php">
    <h4>Please select your Payment Method.</h4>
    <p> 
        <label><input type="radio" name="payment_method" value="0" checked>Prepaid</label>
        <label><input type="radio" name="payment_method" value="1">COD</label> 
    </p>
   
    <div id="pay">
    <label>Total Amount</label>
    <input type="text" id="total_amount"  name='total_amount'  value="100" readonly>

  </div>

  <div id="gttotal"></div>

 <input type="submit" name="">


</form>