In TypeScript, use a type assertion to determine if my object is empty and does not contain any keys defined in the interface

As I review my code, I realize that I have defined an interface as follows:

interface User { 
    name: string,
    age: number
}

I also have a function written like this:

function test(user: User): void { 

}

In addition, I have created an empty object using the same interface:

const user1 = <User>{};
test(user1);

Surprisingly, my code is compiling even though the empty object does not contain the keys specified in the interface. This leaves me wondering how I can enforce compilation errors if the object is missing the required interface keys.

Answer №1

<Person>{} represents a type assertion in TypeScript, where you explicitly declare the type of a variable to the compiler. By using this, you are confirming that the object is indeed of type Person. As a result, TypeScript will not raise any errors.

If you want TypeScript to detect potential coding mistakes, you can do so by writing:

const person1: Person = {};

This way, TypeScript will flag an error for you to address. Check out this resource for further explanations.

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