A very simple example of communication javascript <-> flash:
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<%= swf_tag("example", :width => 400, :height => 300, :mode => :dynamic, :id => "my_flash", :flashvars => {:message => 'Hello, World!'}, :parameters => {:allowScriptAccess => "always", :scale => "showall"}, :javascript_class => "ExampleClass") %>
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<button onclick = "$('#my_flash')[0].sendFlash('Hello from js...')">Say Hello!</button>
<button onclick = "$('#my_flash')[0].say('hi!')">Use javascript class to say hi!</button>