user_nav.html

{{#if user}}
  <%= link_to '{{ user.name }}', "{{ user.profile_path }}" %>
{{else}}
  <%= link_to 'Login', new_session_path %> | <%= link_to 'Sign Up', new_user_path %>
{{/if}}

user_nav.json

{
  user: {
    name: "Zane",
    profile_path: "/users/1"  
  }
}