Problem with RadioButton AutoPostback

Dear Friends,
I am trying to show/hide a div on the check/uncheck of a radiobutton.

For this I have written the following js code.

function init() {

 var radio6 = document.getElementById('<%=RadioButton6.ClientID%>');
         //radio1.checked = 1;
         if (radio6.checked == 0) {
             {
                 document.getElementById('qbuild').style.display = "none";
             }
         }
         
         if (radio6.checked == 1) {
      ...