Is vaadin Ui components compiled into Javascript at run-time?

I am using vaadin components e.i. Gridlayout , label,buttons in my UI screens. I would like to know-- how these components are being rendered in the browser – is it (conversion of vaadin components into javascript) happening at run-time or during the deployment of vaadin project … … …

Yours comments will be highly appreciated

Thanks in advance.

No, it happens when compiling a widgetset. If not using any custom client side code, you can use the default widgetset which comes precompiled in the JAR. Widgets are instantiated on the client side based on the UI “structure” and changes sent from the server.

See e.g.
architecture overview
client side engine
chapters in the book - the latter also gives a little information about the communication.