LUA

Lua

Lightweight. Fast. Embeddable.

Lua is a small, fast scripting language designed to be embedded in other programs. It's the language behind Roblox scripting, and is also used in game engines, config systems, and embedded environments.

Used for

Roblox scripting
Game modding
Embedded systems
Config scripting
Game engines

You'll learn

Variables & types
Strings & numbers
Tables
Functions
Conditions
Loops
Modules
Roblox basics

Code on a screen representing Lua scripting

Fundamentals

Core concepts

Variables and types

Lua uses dynamic typing — variables have no declared type, the value has a type. Use local to scope a variable to the current block. Without local, variables are global, which causes bugs in larger scripts.

variables.lua

-- Local variables (always prefer these)
local name = "Sibah"
local age = 17
local isActive = true
local nothing = nil

-- Type checking
print(type(name))     -- string
print(type(age))      -- number
print(type(isActive)) -- boolean
print(type(nothing))  -- nil

-- String concatenation
local greeting = "Hello, " .. name
print(greeting)       -- Hello, Sibah

Tables

Tables are Lua's only data structure. They work as arrays, dictionaries, objects, and more. An array-style table uses numeric indices starting at 1 (not 0 like most languages). Dictionary-style tables use string keys.

tables.lua

-- Array-style table
local fruits = {"apple", "banana", "cherry"}
print(fruits[1])   -- "apple" (index starts at 1!)
print(#fruits)     -- 3 (length)

-- Add item
table.insert(fruits, "mango")

-- Dictionary-style table
local player = {
  name = "Sibah",
  level = 10,
  alive = true
}

print(player.name)     -- "Sibah"
print(player["level"]) -- 10

-- Mixed table
local data = {
  "first",
  key = "value",
  nested = { x = 1, y = 2 }
}

Functions

Functions in Lua are first-class values — you can store them in variables, pass them to other functions, and return them. Lua functions can return multiple values at once, which is used heavily in Roblox APIs.

functions.lua

-- Basic function
local function add(a, b)
  return a + b
end

-- Assigned to variable
local multiply = function(a, b)
  return a * b
end

-- Multiple return values
local function getCoords()
  return 10, 20, 5  -- x, y, z
end

local x, y, z = getCoords()
print(x, y, z)  -- 10  20  5

-- Variadic functions
local function sum(...)
  local total = 0
  for _, v in ipairs({...}) do
    total = total + v
  end
  return total
end

print(sum(1, 2, 3, 4))  -- 10

Conditions

Lua uses if/elseif/else/end — note the end keyword that closes blocks. Lua treats nil and false as falsy; everything else (including 0 and empty string) is truthy. This is different from JavaScript.

conditions.lua

local score = 85

if score >= 90 then
  print("A grade")
elseif score >= 80 then
  print("B grade")
elseif score >= 70 then
  print("C grade")
else
  print("Below C")
end

-- Logical operators
local isAdmin = true
local isOnline = false

if isAdmin and isOnline then
  print("Active admin")
elseif isAdmin or isOnline then
  print("Partially active")
else
  print("Inactive")
end

Loops

Lua has four loop types. Numeric for iterates a range. Generic for with ipairs iterates arrays. Generic for with pairs iterates all table keys. while and repeat/until loop on conditions.

loops.lua

-- Numeric for loop
for i = 1, 5 do
  print(i)  -- 1, 2, 3, 4, 5
end

-- With step
for i = 10, 1, -2 do
  print(i)  -- 10, 8, 6, 4, 2
end

-- ipairs: array iteration (1-indexed, stops at nil)
local fruits = {"apple", "banana", "cherry"}
for index, value in ipairs(fruits) do
  print(index, value)
end

-- pairs: all table keys
local player = { name = "Sibah", level = 10 }
for key, value in pairs(player) do
  print(key, value)
end

-- while
local count = 0
while count < 5 do
  count = count + 1
end

Modules

Lua modules are just tables returned from a file. require() loads a module and caches it. In Roblox, ModuleScript is the equivalent — a script that returns a table of functions for other scripts to use.

modules.lua

-- mymodule.lua
local M = {}

function M.greet(name)
  return "Hello, " .. name
end

function M.add(a, b)
  return a + b
end

return M

-- main.lua
local mymodule = require("mymodule")

print(mymodule.greet("Sibah"))  -- Hello, Sibah
print(mymodule.add(3, 4))       -- 7

Roblox basics

In Roblox, Lua scripts interact with the game engine through services. game:GetService() gets an engine service. Instance.new() creates a new object. The hierarchy is: game > Workspace/Players/etc > parts, scripts, etc.

roblox.lua

-- Get services
local Players = game:GetService("Players")
local RunService = game:GetService("RunService")

-- When a player joins
Players.PlayerAdded:Connect(function(player)
  print(player.Name .. " joined!")

  -- Wait for character to load
  local character = player.CharacterAdded:Wait()
  local humanoid = character:WaitForChild("Humanoid")

  humanoid.Died:Connect(function()
    print(player.Name .. " died")
  end)
end)

-- Create a part
local part = Instance.new("Part")
part.Size = Vector3.new(4, 1, 4)
part.Position = Vector3.new(0, 5, 0)
part.BrickColor = BrickColor.new("Bright red")
part.Parent = workspace

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