Summary - Special types

Write a program comparing any, unknown, never, and void types.

Summary - Special types

Special types serve different purposes: any disables type checking, unknown allows use after a type check, never marks unreachable code, and void indicates functions that return no value. Choosing the right type improves code safety and readability.

function logla(m: string): void { console.log(m); }
let veri: unknown = "test";
if (typeof veri === "string") { logla(veri); }

Special types provide TypeScript's balance of flexibility and safety.

Exercise void and unknown together

Define a function named goster with a mesaj parameter of type string and return type void. The function should print mesaj with console.log. Declare a variable named veri of type unknown with value "test". Use typeof to check if it is a string; if so, call goster with veri.

Show example solution

function goster(mesaj: string): void {
    console.log(mesaj);
}
let veri: unknown = "test";
if (typeof veri === "string") {
    goster(veri);
}

Test yourself

Which return type is suitable for a function that always throws an error?
- unknown
- void
- any
- never
Show answer

never — A function that always throws an error does not end normally; therefore the correct return type is <code>never</code>. <code>void</code> is for functions that end normally.

Choose the correct type

function isle(deger: ____) { if (typeof deger === "string") { console.log(deger); } }

Show answer

function isle(deger: unknown) { if (typeof deger === "string") { console.log(deger); } }

Special types summary

any

Disables type safety
unknown

Requires check for safe use
never

Function never returns
void

Performs action, no value

Next lesson: Variable annotation

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies