html - Javascript Radio Buttons Functionality bug -

i'm try couple things radio buttons form, , i'm having lot trouble. there 2 radio buttons right now, work together. want have 3 scenarios form.

1. neither of radio buttons checked, hide or disable 2 other elements. (text box , dropdown list)
2. the first radio button checked, hide or disable 1 element.
3. the second radio button checked, hide or disable 1 element.

in 3 scenarios need form return values user, whether nothing, or radio button check , element available radio button. please keep in mind form contain other radio buttons later on separate these. mention want keep in plain javascript if possible.

currently i'm trying use .disable , .checked, not luck. please me figure out. please include explanation of answer if possible can understand it.

here forms code :

<input type="radio" name="clubmember" id="member" value="member" />club member  <input type="radio" name="clubmember" id="nonmember"value="nonmember" />non member <br /> <br />  select club. <select name="clublist"> <option value="cluba">club a</option>  <option value="clubb">club h</option> </select><br />  <!-- or --> club, or guest? <br /> <textarea rows="5" cols="25" name="nonclubinfo">briefly explain here </textarea>  <button type="submit" onclick="return validateregistrationform()" >register</button> 

here code script :

function validateclubinfo() {     if(document.getelementbyid("member").checked == false && document.getelementbyid("nonmember").checked == false)     {         document.getelementbyid("clublist").disabled = true;         document.getelementbyid("nonclubinfo").disabled = true;         alert("this test");         return true;     }     else if(document.getelementbyid("member").checked == true)     {         document.getelementbyid("nonclubinfo").disabled = true;         return true     }     else if(document.getelementbyid("nonmember").checked == true)     {         document.getelementbyid("clublist").disabled = true;         return true;     } } 

i should note validation gets checked through second function, left out because long function , has nothing problem.

at rate on matter appreciated.

it looks problem you're using document.getelementbyid find select/textarea, haven't assigned ids elements. try adding id this:

<select name="clublist" id="clublist>     <option value="cluba">club a</option>      <option value="clubb">club h</option> </select><br />