Is it possible to replicate a type in TypeScript using echo?

Is there any equivalent in TypeScript to the following code snippet?

type TypeA = { x: number };
printType(TypeA);

I have found a method that consistently enables TypeScript to provide a type description.

const y = {
    x: 1,
    z: 'hello',
};

const z: never = y;

Whenever attempting to assign to a never type, an error message is generated which includes details about the type of the value being assigned.

Type '{ x: number; z: string; }' is not assignable to type 'never'.

This technique does have limitations as it necessitates the use of a tangible variable.

Are there any alternative methods available?

typescript

Answer №1

During runtime, it is impossible to validate TypeScript types as they are erased at that point. The only way to enforce type checking is through your IDE or during the compilation process before TypeScript is converted into executable JavaScript code. Your method of generating a compilation error is effective because it occurs during the compile stage; there is no official way to achieve this at runtime with TypeScript.

Fortunately, tools like tsserver have made it easier for various IDEs to incorporate type information seamlessly. Microsoft's Visual Studio Code, in particular, offers features like IntelliSense and inlay hints for better development experience.

Add-ons such as Twoslash enable developers to request inline display of types within their IDEs. This functionality works similarly to inlay hints but allows users to selectively choose which points to display type info for. Twoslash support is integrated into TypeScript Playground and can be added to VSCode via available extensions.

const a = { b: 3, c: "hello" };

console.log(a);
//          ^? [const a: { b: number, c: string }]

Similar to the example shown in this playground link, the square bracketed type annotation updates automatically as you modify the code.

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