app/views/locations/create.js.erb
<% if @location.errors.any? %>
$(".alert span").html("<%=j @location.errors.to_a.to_sentence %>");
$(".alert").addClass("alert-danger").slideFadeToggle('fast');
<% else %>
$(".alert span").html("Updated!");
$(".alert").addClass("alert-success").slideFadeToggle('fast');
<% end %>