Comments

Comments allow us to add explanations and notes to our code. When scripts are executed all comments are completely ignored.

Single-Line Comment

You can use the hotkey Ctrl + / in Roblox Studio to create a comment on the current line.

-- This is a single-line comment
local score = 100 -- This single-line comment is at the end of a line

Multi-Line Comment

--[[
This is a multi-line comment.
You can write multiple lines of comments here.
]]

Variables

Variables are used for storing data of different types.

local nameOfVariable = "valueOfVariable"

• local is the scope of the variable.
• nameofVariable is the name of the variable.
• "valueOfVariable" is the value of the variable.

Data Types

A variable’s type is based off its value. The type of a variable is important as it enables us to know how we can use that variable. For instance, you can only perform math operations on two number variables.

Primitive Types

The following are standard Luau types, which are also commonly used in other programming languages.

String

You can combine two strings putting two periods (..) between the strings.

local newString = "Hey I'm".." pretty cool!" -- Hey I'm pretty cool!

Using backticks (`) when creating a string is another easy way of combining strings.

local firstString = "Hey I'm"
local newString = `{firstString} pretty cool!` -- Hey I'm pretty cool!

Number

You can perform math operations with two numbers by using any arithmetic symbols between the numbers.

local newMath = 5 + 10 -- 15

Boolean

You can use a conditional statement to create a boolean.

local newBool = 5 + 10 == 15 -- true

Roblox Types

Roblox adds to their plethora of custom types often, but you always view the most up to date list here!

Examples

Simple

local numberVariable = 10
local stringVariable = "100"
local booleanVariable = true
local nilVariable = nil
local nilVariable2
local tableArrayVariable = {"2", 3, true}
local tableDictionaryVariable = {first = "2", 2 = "3rd", third = "two"}

Advanced

local numberVariable = 1_000 -- _ can be used within a number to improve readability of larger numbers
local stringVariable = "100".." and two"
local stringVariableTwo = `Here's another string and the first string: {stringVariable}`
local booleanVariable = numberVariable == 1_000
local nilVariable = nil
local nilVariable2 = nilVariable or nil

Functions

Functions are reusable blocks of code that perform specific tasks.

-- Defining a function
function greetPlayer(playerName)
    print("Hello, " .. playerName)
end

-- Calling a function
greetPlayer("Alice")

Conditional Statements

We can use conditionals to perform an action based on a specified scenario.

Conditionals are written in the following format:

local number = 10
if number == 10 then -- Can be thought of as 10 = 10
    print(true)
elseif number < 15 then -- Can be thought of as 10 is less than 15
    print(true)
else -- Can be thought of as any other 'condition' besides the previous two
    print(false)
end

Conditionals are read from top to bottom. For example, first number == 10 is read, since this is true print(true) will run, and nothing more will happen. If we want number < 15 to be checked, we must use a number between 11 and 14 so that number == 10 will NOT be true.

Relational Operators

We commonly use relational operators to create conditionals.

if 10 == 10 then -- Can be thought of as 10 = 10 (True)
    print(true)
end

Logical Operators

We can also use logical operators to create slightly more complex conditionals.

if not 10 == 10 or not 1 == 1 then -- Can be thought of as 10 ~= 10 or 1 ~= 1 (False)
    print(true)
end

Tables

Tables are used to store a collection of data.

Arrays

Arrays are used to store a collection of values in a specific order. Elements in an array are indexed with integers starting at 1.

local fruits = {"apple", "banana", "cherry"}

Adding values to an Array

We can use the table.insert function to add values to the end of an array.

table.insert(fruits, "grape")

Removing Values from an Array

We can use the table.remove function to remove a value by index.

local fruits = {"apple", "banana", "cherry"}
table.remove(fruits, 2) -- Removes "banana"

Using Values from an Array

We can use elements from an array by using their index.

local fruits = {"apple", "banana", "cherry"}
local firstFruit = fruits[1] -- "apple"

Dictionaries

Dictionaries are used to store key-value pairs. These could be thought of as storing variables, where they key would be the variable’s name and the value would be the variable’s value.

local player = {
    name = "Bob",
    score = 75
}

Adding Values to a Dictionary

You can add values to dictionaries by indexing it with the dot operator and then specifying the new key and value.

player.level = 10

Removing Values from a Dictionary

You can remove values from dictionaries by setting the value of the key to nil.

player.score = nil -- Removes the "score" key and value

Using Values from a Dictionary

You can use values from dictionaries simply dot indexing it with the specific key.

local playerName = player.name -- "Bob"

Loops

Loops allow us to execute a block of code repeatedly.

For Loops

For loops are the most commonly used loops. We use these when we know the total number of iterations in advance or if we want to iterate through a table.

Numeric For Loop

for i = 1, 5 do
    print(i) -- Prints numbers from 1 to 5
end

Iterating over an Array

Elements are stored inside of an array in a specific order start from the index of 1. As we iterate through the following array the elements will be printed in the following order: apple, banana, cherry.

local fruits = {"apple", "banana", "cherry"}

for index, value of fruits do
    print(index, value) -- Prints the index beside the fruit
end

Iterating over a Dictionary

One important thing to keep in mind is that key value pairs are stored inside of dictionaries in no specific order. That means as we iterate through the dictionary, the score 75 pair could be printed before the name bob pair.

local player = {
    name = "Bob",
    score = 75
}

for key, value of player do
    print(index, value) -- Prints the key beside the value
end

While Loops

While loops are used when the number of iterations isn’t known in advance but is based on a condition.

The following while loop will iterate until the counter variable becomes 5.

local counter = 1

while counter <= 5 do
    print(counter) -- Prints numbers from 1 to 5
    counter = counter + 1
end

Controlling Loops

We can modify the behavior of loops such as stopping them early or skipping the current iteration by using control statements.

Break

The break statement is used to stop the loop prematurely.

for i = 1, 10 do
    if i == 5 then
        break -- Exits the loop when i equals 5
    end
end

local counter = 10

while true do
  if counter == 10 then
    break -- Exits the loop during the first iteration
  end
  
  print(true) -- Will never be printed as the iteration is stopped before this is reached
end

Continue

The continue statement is used to skip the current iteration.

local fruits = {"apple", "banana", "cherry"}

for index, value of fruits do
  if value == "banana" then
    continue
  end
  
  print(value) -- Only apple and cherry will be printed
end

Loop Tips

Infinite Loops

There are occasions where you may want a code block to be executed during the entire duration of your game being active. This is possible by using a while loop and never breaking the condition. The simplest way to do this is by setting true as the condition.

Depending on the situation we might be able to avoid using an infinite loop by instead using event driven programming. It’s often recommended to avoid infinite loops because they can easily be misused and really stagger your game’s performance.

while true do
  print(true) -- This will never stop being printed
end

Yielding in Loops

It’s almost always recommended to use the task.wait function inside of a while loop to prevent performance impacts. This function allows us to yield or temporarily stop the loop after each iteration.

while true do
  print(true) -- True will infinitely be printed each second
  task.wait(1) -- Yield / pause control for 1 second
end

Symbols