Lazy loading with Y.use()

gistfile1.js

YUI().use('foo', function (Y) {
  // ... do stuff with foo ...

  // When you need to load "bar", call Y.use() and use it inside the
  // callback. The difference between YUI().use() and Y.use() is that
  // the first creates a new YUI instance, whereas the second adds
  // "bar" to the existing instance.
  Y.use('bar', function () {
      // ... do stuff with bar ...
  });
});