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Number, String and Boolean

Part of the Introduction To Luau section of Coddy's Lua journey. Lesson 6 of 80.

Luau has three fundamental primitive types that form the building blocks of most programs: string, number and boolean. You've been using these values in Lua all along: Luau lets you declare them as types.

The string type is for text data:

local productName: string = "Laptop"

The number type handles all numeric values: integers and decimals alike, just as you know from Lua's single number type:

local price: number = 999.99

The boolean type represents true/false values, perfect for flags and conditions:

local inStock: boolean = true

Once annotated, each variable is held to its type: assign the string "500" to price and the type checker complains immediately. And remember: print(inStock) prints the word true, because booleans stringify to true/false.

challenge icon

Challenge

Easy

Describe a product with three typed variables.

  1. Declare local productName: string = "Gaming Mouse".
  2. Declare local price: number = 49.99 and local inStock: boolean = true.
  3. Print the three variables, one per line, in that order.

Press Run Code: the output shows Gaming Mouse, 49.99 and true.

Try it yourself

-- 1) declare productName, price and inStock with their types
-- 2) print all three, each on its own line

All lessons in Introduction To Luau

1Getting Started with Luau

What Is Luau?Why Use Luau?Your First Luau CodeType Checking & Error ModesRecap: Introduction to Luau

4Working with Functions

Typing Params & Return ValuesTyping Anonymous FunctionsFunctions Returning NothingOptional ParametersDefault Parameter ValuesDefaults for BooleansVariadic FunctionsDefining Function TypesRecap: Typed Functions

7Project: Typed Task Manager

Project: The Task ShapeFunction to Add a TaskProject lessonFunction to Change Task StatusProject lessonFunction: List Tasks by StatusProject lessonFunction: Print Task SummaryProject lessonCommand Loop: AddProject lessonCommand Loop: List and DoneProject lessonCommand Loop: SummaryProject lesson

10Project: Generic Inventory

Project: Inventory ItemFunction: Add ItemsProject lessonThe Weapons ListProject lessonFunction: Find Item By IDProject lessonSpecific Inventory TypesProject lessonFunction: Describe ItemsProject lessonAnswer Item QueriesProject lesson

2Core Types

Number, String and BooleanThe 'any' Type: Escape HatchThe 'unknown' TypeNil & Optional TypesType Inference in ActionExplicit Type AnnotationsRecap: Core Types Practice

5Aliases, Unions, Intersections

Type Aliases for PrimitivesUnion TypesWorking with Union TypesLiteral TypesIntersection TypesCombining Type AliasesRecap: Advanced Type Combos

8Enums, the Luau Way

The Enum Pattern in LuauNumeric Enums with TablesString Enums as UnionsUsing Literal Union EnumsFreezing Constant TablesRecap: Enums, the Luau Way

11Advanced Topics

Type AssertionsType Guards With typeofThe never TypeNil Safety In Strict ModeIndex SignaturesRecap: Config Value TypesRecap: Fine-Tuning Types

3Typed Tables: Arrays & Maps

Typed ArraysAdding and Reading ElementsWhat is a Map Type?Declaring and Accessing MapsIterating TablesMixed-Shape TablesReading a GridBuilding a Gridtable.unpackRecap: Arrays and Maps

6Typing Table Shapes

Inline Shape AnnotationsType Aliases for ShapesOptional PropertiesShapes vs. Loose TablesExtending ShapesAdding Methods to ShapesSelf and Colon MethodsRecap: Defining Table Shapes

9Generics: A First Look

The Problem Generics SolveA Generic Identity FunctionUsing a Generic FunctionGeneric ArraysGeneric Type AliasesRecap: Generic Functions

Practice on your own: Online Luau compiler