setting radio button checked property using js code example

Example 1: html radio button checked

<input type="radio" id="huey" name="drone" value="huey"
         checked> 
<!-- https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/radio-->

Example 2: javascript radio button value if checked

//alert(document.querySelector('input[name = "comp"]:checked').value);

$test=document.querySelector('input[name = "comp"]:checked').value;

if($test="silver") {
        amount=50;
    }else if($test="gold") {
      amount=90;
    }else{
      amount=30;
    }