change post-specific <button> tag's text

change post-specific <button> tag's text

Hello guys. i just registered here. i have many posts in index page. and each post located in <li> tag. 

  1. <ul>
  2.       <li class="class_li" data-id="this_posts_id">
  3.             < href="#" class="btn">Vote Up</a> 
  4.             <button class="btn dropdown-toggle"  data-toggle="dropdown"><span                                               class="vote"> VOTE </span><span class="caret"></span></button>
  5.       </li>
  6.       <li class="class1" data-id="this_posts_id">
  7.             <!-- another <li> for other posts with same tags and class names -->
  8.       </li>
  9. </ul>
and jquery part:

  1. $('a.btn').click( function(){
  2.         var post_id = $(this).closest('li').data('id');
  3.         var button = $('button.btn.dropdown-toggle').find('.vote').text('something here'); // this part doesn't work..
my problem is i cant reach span which under button tag. actually i tried many ways. but i only can change all post's vote in the page. i need reach THIS <li> tag's span. like how i got post_id.

i am stuck. tryin to make it for hours :(

thank you :)