resetting input radio value in my .js.erb

I need to reset the values of the input radio in my view , via Ajax

the view has the following generated html <input checked="checked" class="" id="user_membership_selection_1" name="user[membership_selection]" type="radio" value="1" />Selected Membership</p> <input id="user_membership_selection_2" name="user[membership_selection]" type="radio" value="2" /> Selected Membership</p>

fin my controller method , I get other values to replace the radio values "1" => "11" and "2" by "22" I can get easily the values like that alert( $ ('input:radio[name="user[membership_selection]"]:checked').val() );

but I cannot change it.. I thought I could access them like that alert( $('input:radio[name="user[membership_selection]"] [0]').val() ); alert( $('input:radio[name="user[membership_selection]"] [1]').val() ); and reset the value

$('input:radio[name="user[membership_selection]"][0]').val( "11") $('input:radio[name="user[membership_selection]"][1]').val( "22")

as $('input:radio[name="user[membership_selection]"]') should returned an array with the 2 elements .. but it's wrong ... 'undefined'

any clue ??