[Solved] Selection radio button

<script>
    function myFunction() {
        var x = document.getElementsByName('os');
        var rate_value;
        for(var i = 0; i < x.length; i++){
            if(x[i].checked){
                rate_value = x[i].value;
                break;
            }
        }
        document.getElementById("demo").innerHTML = rate_value;

    }
</script>