Just a quick demo of a callback in Lua, inspired by a Discord discussion

callback.lua

local function just_print_it(text)
    print(text)
end

local function print_it_backwards(text)
    print(string.reverse(text))
end

local function do_something(text, callback)
    -- do neat stuff
    callback(text)
end

do_something("hello", just_print_it)

do_something("goodbye", print_it_backwards)