Type Annotation and Inference in TypeScript

A way to assign a default value to a variable

A method to explicitly declare the type of a variable

A feature that automatically assigns types to variables

A way to convert one type into another

When TypeScript automatically determines the type of a variable

When TypeScript forces developers to specify types manually

A process of converting one type to another

A way to disable type checking

number

any

unknown

string

The code compiles and runs without errors

TypeScript throws a compilation error

TypeScript changes the type of x to string

The value is automatically converted to a number

function add(a: number, b: number) -> number {}

function add(a: number, b: number): number {}

function add(a: number, b: number) = number {}

function add(a: number, b: number) returns number {}

void

any

string

unknown

boolean

any

true

unknown

any

undefined

unknown

void

let value: multiple<number, string> = 42;

let value = number | string = 42;

let value: number | string = 42;

let value: any = 42 | "hello";

null and undefined are treated as normal values

null and undefined cannot be assigned to variables of other types unless explicitly allowed

TypeScript ignores null values in type checking

null and undefined behave like numbers