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  • Joseph Vaughan thinks this is interesting:

Rather than the HTML Service used in most of this book, this chapter will focus on the UiApp Service, which is still alive and well in the Google Apps Script ecosystem. If you want a more extensive look at the UiApp Service, I encourage you to also pick up a copy of the first edition of this book, also available from O’Reilly.

From

Cover of Google Apps Script, 2nd Edition

Note

the UiApp service was deprecated in December 2014.