js check if radio button is checked

1$('#element').click(function() {
2   if($('#radio_button').is(':checked')) { alert("it's checked"); }
3});
4

1if(document.getElementById('gender_Male').checked) {
2  //Male radio button is checked
3}else if(document.getElementById('gender_Female').checked) {
4  //Female radio button is checked
5}

1//alert(document.querySelector('input[name = "comp"]:checked').value);
2
3$test=document.querySelector('input[name = "comp"]:checked').value;
4
5if($test="silver") {
6        amount=50;
7    }else if($test="gold") {
8      amount=90;
9    }else{
10      amount=30;
11    }