Data Types

Data types in Luau represent the type of value given to a variable. Luau uses Lua 5.1 as its base meaning- Luau is also a dynamically typed language. So, the type of data is automatically assigned based on the value.

Basic Data Types

Luau supports eight built-in data types from Lua, which are:

• nil: Represent the absence of value or different type value from others.
• boolean: Hold the values true and false.
• number: Contains numerical values.
• string: Hold strings inside single or double quotes as value.
• function: Holds function as its value.
• userdata: Used when Luau needs to have a value in array format.
• thread: Contain threads as its value.
• table: Represent a table.

In addition to these, Luau has enum to represent a fixed list of items.

Type Annotation

In Luau, the data type does not need to be explicitly defined every time a value is assigned to a variable or a function. However, in some cases, the value must be strictly defined for the program to run as expected.

The colon symbol : is used after the name of a variable that is about to be created.

Variable:

local numerator: number = 18

Function:

function divide(numerator: number, denominator: number): number
    return numerator/denominator
end

Type Checking

Luau provides type checking to offer users direct feedback in case of any error related to the data types. There are three available modes:

• --!nocheck: When no check is needed.
• --!nonstrict: This is used by default, it will check the data type but will not directly point it out.
• --!strict: This should be used when direct feedback on type checking is needed. It shows the error and the line that needs to be changed.

Mode should be placed on top of a couple of lines before the program script.

--!strict

local num: number
num = 8

It needs to use the luau-analyze command.

luau-analyze starts.luau

The command above will return nothing because the num variable has number as its value. Otherwise, when the num variable is changed to "8" (string value) it will give the following output:

TypeError: Type 'string' could not be converted into 'number'