How to send arguments in OnEvent?

[Fizzlemizz]

The arguments (payload) part of OnEvent is the ...
It means a variable number of arguments (each event has zero to lots or arguments depending on the event received)

Frame:SetScript("OnEvent", function(self, event, ...)
    local arg1, arg2, arg3 = ...
    print(arg1, arg3)
end)

You can see for the PLAYER_ENTERING_WORLD event, it contains two arguments in its payload, isInitalLogin and isReloadUI so you could:

Frame:SetScript("OnEvent", function(self, event, ...)
    if event == "PLAYER_ENTERING_WORLD" then
        local isInitalLogin, isReloadUI = ...
    elseif event == "BAG_OPEN" then
        local bagID = ...
    end
end)
Frame:RegisterEvent("PLAYER_ENTERING_WORLD")
Frame:RegisterEvent("BAG_OPEN")

for example, to make it more readable what the arguments are for a particular event.