jQuery code for Textbox countdown

_micropost_form.html.erb

<script type="text/javascript">
<!--
 
$('#micropost_content').live('keyup keydown', function(e) {
  var maxLen = 140;
  var left = maxLen - $(this).val().length;
  $('#char-count').html(left);
}); 
//-->
</script>
 
<%= form_for @micropost do |f| %>
  <%= render 'shared/error_messages', :object => f.object %>
  <div class="field">
    <%= f.text_area :content, :maxlength => 140 %>
  </div>
   <div>Characters left: <span id="char-count">140</span></div>
  <div class="actions">
    <%= f.submit "Submit" %>
  </div>
<% end %>