Use an [up-flashes] element to show confirmations, alerts or warnings.

You application layout should have an empty [up-flashes] element to indicate where flash messages
should be inserted:
<nav>
  Navigation items ...
</nav>
<div up-flashes></div> <!-- mark-line -->
<main>
  Main page content ...
</main>
To render a flash message, include an [up-flashes] element in your response.
The element's content should be the messages you want to render:
<div up-flashes>
  <strong>User was updated!</strong>
</div>
<main>
  Main response content ...
</main>
See notification flashes for more details and examples.
The name of a transition to morph between the old and new notification flashes.
The duration of the transition in milliseconds.
The timing function that controls the acceleration of the transition.