void vs never

Written byPhuoc Nguyen

#void

The `void` type represents the absence of a value. It's typically used as the return type for functions that don't return a value.

log.ts

const log = (message: string): void {
    console.log(message);
};

In the example above, the `log` function doesn't give back any value, which means that its return type is `void`.

#never

The `never` type represents the absence of a value that will never occur. It's handy in two scenarios:

When a function always throws an error.

In the following example, the `throwError` function will always throw an error and never return a value.

throwError.ts

const throwError = (): never => {
    throw new Error('Something went wrong');
};

When a function never finishes.

The code inside the `infiniteLoop` function never finishes executing because it contains an endless loop.

infiniteLoop.ts

const infiniteLoop = (): never => {
    while (true) {
        // Do something indefinitely ...
    }
};

When it comes to `void` and `never`, it's important to understand their distinctions. `void` represents the absence of a value that could happen, while `never` represents the absence of a value that will never happen.

To put it simply, `void` is used when a function may or may not return a value, while `never` is used when a function will never return a value.

#See also

any vs unknown

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Phước Nguyễn