How to make a Global Function? [closed]

There are a few ways you can create a global function. The first is simply using _G. _G is a global table that you can put functions inside. The _G table is not completely global though. There is an _G table for the server and then individual _G tables for each client.

function _G.Bobert() --In normal script
print("HI")
end

_G.Bobert() --In another server script

_G.Bobert () --In a local script this will not work unless a local script on the same client defines it.

So to make the function available in every localscript/client you could put this localscript inside StarterGui. So then this script is replicated to every client where the function is defined in every client's _G table.

function _G.Bobert()
print("HI")
end

If you just want a function accessible everywhere you could also use a ModuleScript.

In Module Script:

function ClearGui(Player)

end

return ClearGui

In Another script:

local ClearGui = require(Workspace.ClearGuiModuleScript)

ClearGui(BOBERT)

The way I suggest to do this is not with global variables but rather with a RemoteEvent. These allow you to communicate across scopes (server/client). This allows the server to call one function that then resets all players GUIs. The useful thing about these is that you can fire the function for all clients or for a particular player only.

Server Script:

local remoteEvent = game.ReplicatedStorage.RemoteEvent -- pointer to your remote event object

-- When you want to reset the gui's
-- All Clients
remoteEvent:FireAllClients(...) -- The ... stands for any arguments you may need

-- Single Player
remoteEvent:FireAllClients(player, ...) -- Player needs to be defined

Local Script:

local remoteEvent = game.ReplicatedStorage.RemoteEvent

remoteEvent.OnClientEvent:connect(function()
    -- Do something to make you GUIs reset
    -- You could clear all GUIs then copy new ones in for example
end)