将类添加到菜单中的活动li

Here's my haml code:

这是我的haml代码:

%li.active
  %a{ :href => "#" } Home
%li
  %a{ :href => "#" } About
%li
  %a{ :href => "#" } Sign up
%li
  %a{ :href => "#" } Log in
%li.active