Pure Data has a component loadbangthat does what it says: it sends one hit when the graph starts working. NoFlo core/Kickdoes not send its data until its input is entered INand you can save the IIP bit in noflo-ui.
loadbang
core/Kick
IN
core/Repeatwith IIP (any line) on the port INwill do what you are looking for. Here is an example browser that displays a pop-up warning when starting a network:
core/Repeat
loadbang(core/Repeat) OUT -> IN alert(core/MakeFunction) 'alert("hi");' -> FUNCTION alert ':-)' -> IN loadbang
Related discussion: https://github.com/noflo/noflo-ui/issues/97