What are type predicates in TypeScript?

What are type predicates in TypeScript?

Type predicates are a way to define a specific type for a variable within a function. They help TypeScript understand the type of a variable after a certain condition is met.

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

Sure! Here's a simple example:

function isString(value: any): value is string {
    return typeof value === 'string';
}

const input: any = 'Hello, TypeScript!';
if (isString(input)) {
    console.log(input.toUpperCase()); // This is safe because we know input is a string.
}

What are the benefits of using type predicates?

Type predicates improve type safety and help avoid runtime errors by allowing TypeScript to narrow down types based on conditions.

Are there any limitations to using type predicates?

Yes, type predicates can only be used in function return types and cannot be used in type aliases or interfaces.