simple_bubbling.js

function increment() {
    count++;
}

var a = new Y.EventTarget(),
    b = new Y.EventTarget({
            bubbles: true,
            emitFacade: true, 
            prefix: 'foo'
        }),
    count = 0;

b.addTarget(a);

a.on('foo:bar', increment);
b.on('bar', increment);

b.fire('bar');

alert(count);