Void type for functions in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the void type mean when used as a function's return type in TypeScript?

It means the function does not return any value. The function performs actions but does not give back a result.

beginner

How do you declare a function that returns nothing using void in TypeScript?

You write the function with <code>: void</code> after the parentheses. For example: <br><pre>function greet(): void {<br>  console.log('Hello!');<br>}</pre>

intermediate

Can a function with void return type return null or undefined explicitly?

Yes, it can return undefined explicitly but not null. Usually, functions with void return type do not return anything at all.

beginner

What happens if a function declared with void return type tries to return a value?

TypeScript will show an error because the function promises not to return any value, but a value is returned.

beginner

Why is using void useful in TypeScript functions?

It helps to clearly show that the function is only for doing something (like printing or changing data) and not for producing a value. This makes code easier to understand.

What does a function with return type void do?

A Returns nothing

B Returns a value

C Returns a string

D Returns a number

A function with return type void does not return any value.

Which of these is a correct way to declare a void function in TypeScript?

A function sayHi(): void { console.log('Hi'); }

B function sayHi(): string { console.log('Hi'); }

C function sayHi() { return 'Hi'; }

D function sayHi(): number { return 5; }

Only option D declares a function that returns nothing (void) and just prints a message.

What error occurs if a void function tries to return a value?

A No error

B TypeScript error: Type 'value' is not assignable to type 'void'

C Runtime error

D Syntax error

TypeScript shows a type error because the function promises not to return a value.

Can a void function explicitly return undefined?

A No

B Only if it returns a string

C Yes

D Only if it returns a number

A void function can explicitly return undefined, but usually it returns nothing.

Why use void as a function return type?

A To indicate the function returns an object

B To indicate the function returns a string

C To indicate the function returns a number

D To indicate the function returns nothing

void means the function returns nothing, helping make code intentions clear.

Explain what the void type means for a function's return type in TypeScript and why it is useful.

Think about what happens when a function does not give back any result.

Describe what happens if you try to return a value from a function declared with void return type.

Consider TypeScript's type checking rules.