void vs never
Written byPhuoc Nguyen
Created
24 Aug, 2023
Category
TypeScript
TypeScript has two types,
`never` and `void`, which represent the absence of a value. While they may seem similar, it's important to know the key differences between them. Let's dive in and explore!#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 ...
}
};#Differences
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
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Phước Nguyễn