Void type for functions in Typescript

Introduction

The void type shows that a function does not return any value. It helps us know when a function just does something but does not give back a result.

When a function only prints a message and does not return anything.

When a function changes something but does not need to send back a value.

When you want to make clear that a function's job is to do an action, not to calculate.

When you want to avoid accidentally returning a value from a function.

When writing event handlers that just react to events without returning data.

Syntax

Typescript

function functionName(): void {
  // code here
}

The void type goes after the parentheses () and a colon :.

If you forget void, TypeScript may assume the function returns any or undefined.

Examples

This function prints a message and returns nothing.

Typescript

function sayHello(): void {
  console.log('Hello!');
}

An arrow function that logs a number and returns nothing.

Typescript

const logNumber = (num: number): void => {
  console.log(num);
};

A function that does nothing and returns nothing.

Typescript

function doNothing(): void {
  // no return statement here
}

Sample Program

This program defines a function that greets a person by name and prints the greeting. It does not return any value.

Typescript

function greet(name: string): void {
  console.log(`Hello, ${name}!`);
}

greet('Alice');

Important Notes

If a function has void type, it can still return undefined explicitly or just end without a return.

Using void helps other programmers understand the function's purpose quickly.

Summary

void means a function does not return a value.

Use it to show a function only does something but does not give back data.

It helps keep code clear and avoid mistakes with unexpected return values.