TypeScript void Type

In this tutorial, you will learn about the TypeScript void type and how to use it as the return type of functions that do not return any value.

Introduction to TypeScript void type

The void type denotes the absence of having any type at all. It is a little like the opposite of the any type.

Typically, you use the void type as the return type of functions that do not return a value. For example:

function log(message): void {
    console.log(messsage);
}

It is a good practice to add the void type as the return type of a function or a method that doesn’t return any value. By doing this, you can gain the following benefits:

1. Improve clarity of the code: you do not have to read the whole function body to see if it returns anything.
2. Ensure type-safe: you will never assign the function with the void return type to a variable.

Notice that if you use the void type for a variable, you can only assign undefined to that variable. In this case, the void type is not useful. For example:

let useless: void = undefined;
useless = 1; // error

If the --strictNullChecks flag is not specified, you can assign the useless to null.

useless = null; // OK if --strictNullChecks is not specified

Conclusion

Use the void type as the return type of functions that do not return any value.