Lua Scripting Basics: Variables, Tables & Functions

Lua is a lightweight, fast scripting language that powers game logic in Roblox and many other platforms. Whether you are brand new to programming or coming from another language, understanding Lua’s fundamentals will help you read, write, and request scripts with confidence. This guide walks you through the essential concepts you will encounter in almost every Lua script.

Variables and Data Types

In Lua, you declare variables with the local keyword. Lua is dynamically typed, so you do not need to specify a type — the value itself determines it.

-- Numbers
local score = 0
local speed = 16.5

-- Strings
local playerName = "Virus"

-- Booleans
local isAlive = true

-- Nil (the absence of a value)
local empty = nil

Lua’s core data types are number, string, boolean, nil, table, and function. You will use all of them regularly.

Functions

Functions let you group reusable logic under a name. You can define them with local function (scoped) or as values assigned to a variable.

local function greetPlayer(name)
    print("Welcome, " .. name .. "!")
end

greetPlayer("Virus") -- Output: Welcome, Virus!

-- Functions as values
local square = function(n)
    return n * n
end

print(square(5)) -- Output: 25

Tables

Tables are Lua’s only data structure — they act as both arrays and dictionaries (key-value maps). They are the backbone of almost every Roblox script.

-- Array-style table
local fruits = { "apple", "banana", "cherry" }
print(fruits[1]) -- Output: apple  (Lua arrays start at 1!)

-- Dictionary-style table
local player = {
    name = "Virus",
    level = 42,
    isAdmin = false,
}
print(player.name)    -- Output: Virus
print(player["level"]) -- Output: 42

-- Adding a new key
player.coins = 500

Loops

Lua provides for, while, and repeat...until loops for iteration.

-- Numeric for loop: counts from 1 to 5
for i = 1, 5 do
    print("Count: " .. i)
end

-- Generic for loop: iterates over a table
local colors = { "red", "green", "blue" }
for index, color in ipairs(colors) do
    print(index, color)
end

local lives = 3

while lives > 0 do
    print("Lives remaining: " .. lives)
    lives = lives - 1
end

local input = 0

repeat
    input = input + 1
until input >= 3

print("Stopped at: " .. input) -- Output: Stopped at: 3

Conditionals

Use if, elseif, and else to branch your logic. Lua uses and, or, and not instead of &&, ||, and !.

local health = 75

if health <= 0 then
    print("You are dead.")
elseif health < 25 then
    print("Critical health — find cover!")
elseif health < 75 then
    print("You are wounded.")
else
    print("You are at full health.")
end

-- Combining conditions
local hasKey = true
local doorOpen = false

if hasKey and not doorOpen then
    print("Use your key to open the door.")
end

String Concatenation and Length

Lua uses .. to join strings and # to get the length of a string or array-style table.

local first = "Hello"
local second = "World"
print(first .. ", " .. second .. "!") -- Output: Hello, World!

local items = { "sword", "shield", "potion" }
print("You have " .. #items .. " items.") -- Output: You have 3 items.

Common Lua gotchas to watch out for:

Arrays start at 1, not 0. myTable[1] is the first element.
nil is not the same as false. nil means “no value exists”; false is a boolean. Both are falsy in conditions, but they are different types.
There is no null keyword — use nil instead.
~= means “not equal”, not != like in most other languages.
Global variables are dangerous. Always use local unless you have a specific reason not to — accidental globals cause hard-to-find bugs.
String concatenation with .. requires spaces around it to avoid ambiguity with decimal numbers.

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Lua Scripting Basics: Variables, Tables & Functions

Variables and Data Types

Functions

Tables

Loops

Conditionals

String Concatenation and Length

Keep Learning

Roblox Scripting

Debugging Tips

​Variables and Data Types

​Functions

​Tables

​Loops

​Conditionals

​String Concatenation and Length

​Keep Learning

Roblox Scripting

Debugging Tips

Variables and Data Types

Functions

Tables

Loops

Conditionals

String Concatenation and Length

Keep Learning