What are type assertions in TypeScript?

What are type assertions in TypeScript?

Type assertions in TypeScript allow you to override the inferred type of a variable. It's a way to tell the compiler, 'Trust me, I know what I'm doing.' You can use the as keyword or angle-bracket syntax to assert a type.

Can you give me an example of how to use type assertions?

Sure! Here's a simple example:

let someValue: unknown = 'this is a string';
let strLength: number = (someValue as string).length;

In this case, we assert that someValue is a string so we can access its length property.

Are there any risks associated with using type assertions?

Yes, using type assertions can lead to runtime errors if you're wrong about the type. It's important to ensure that the value actually matches the asserted type to avoid issues.

When should I use type assertions?

You should use type assertions when you're certain about the type of a variable but TypeScript can't infer it correctly. However, use them sparingly to maintain type safety.