haml_scrach.js

new Haml('userbar', function (params, render, use) {
  
  with (params) {
    this.use({
      user: user.merge({full_name: user.first_name + ' ' + user.last_name}),
      session: session
    });
  }
  
  this.setOptions({
    box_class: 'paid'
  });
  
  this.use('date', Date());
  
  // in haml available: params, this, options, hash passed in use
  
  this.render('
    #userbar.right.{options.box_class}
      %img.userpic@src={user.pic.small}/
      %span.username= {user.full_name}
      %a.logout(href="/sessions/{session.id}" method="delete")= "logout"
  ');
});

Haml.userbar({user: User.find(30), session: Session.current})
  .injectTo(document.body);

Haml.template('userbar');